Who are Philosophers from The Age of Reason?

The Age of Reason period of the Modern era of philosophy is generally regarded as the start of modern philosophy, and roughly equates to the 17th Century.

It includes the following major philosophers:

Hobbes, Thomas (1588 – 1679) English
Descartes, René (1596 – 1650) French
Pascal, Blaise (1623 – 1662) French
Spinoza, Baruch (1623 – 1677) Dutch-Jewish
Locke, John (1632 – 1704) English
Malebranche, Nicolas (1638 – 1715) French
Leibniz, Gottfried Wilhelm (1646 – 1716) German

The Age of Reason saw a continuation of the move away from theology and faith-based arguments, and marks the shaking off of medieval approaches to philosophy such as Scholasticism, in preference for more unified philosophical systems like Rationalism and British Empiricism. The advances in science, the growth of religious tolerance and the rise of philosophical liberalism also led to a revival in Political Philosophy in general.

Along with the Age of Enlightenment of the 18th Century, which the Age of Reason gave rise to, it is also know as the Early Modern period.


Gottfried Wilhelm Leibniz (1646 – 1716)


Gottfried Wilhelm LeibnizGottfried Wilhelm Leibniz (also Leibnitz or von Leibniz) (1646 – 1716) was a German philosopher, mathematician, scientist and polymath of the Age of Reason.

As a philosopher, he was, along with René Descartes and Baruch Spinoza, a major figure in the Continental Rationalism movement (the main 17th Century opposition to the British Empiricist school of thought of HobbesLocke, Berkeley and Hume). He devised his rather eccentric metaphysical theory of monads operating in a pre-established divine harmony in order to overcome what he saw as some of the drawbacks of the theories of Descartes and Spinoza. He remained a devout Christian throughout his life and his formulation of the Problem of Evil in a world created by a good God was an influential one.

His contributions to Logic were perhaps the most important between Aristotle and the developments in modern formal Logic of the mid-19th Century, and to some extent he anticipated modern Symbolic Logic.

He is equally important in the history of mathematics, as the inventor of calculus(independently of Sir Isaac Newton), and as the discoverer of the binary system (the foundation of virtually all modern computer architectures). He also made major contributions to physics, and anticipated notions that surfaced much later in other sciences biology, medicine, geology, probability theory, psychology, linguistics and information science, as well as writing on politics, law, ethics, theology, history and philology.


Leibniz (pronounced LIBE-nitz) was born on 1 July 1646 in Leipzig in Saxony, eastern Germany. His father, Friedrich Leibniz, died when Gottfried was just six years old, so he mainly learned his religious and moral values from his mother, Catherina Schmuck (the daughter of a lawyer and Friedrich’s third wife). However, his father, who had been a Professor of Moral Philosophy at the University of Leipzig, left his personal library to his son, who was granted free access to it from age seven onwards, in addition to attending the regular Nicolai School in Leipzig.

By twelve, he had taught himself Latin, which he used freely all his life, and had begun studying Greek. At 14, he entered the University of Leipzig, mastering the standard university courses in classics, law, Logic, and Scholastic and Aristotelian philosophy under Jakob Thomasius (1622 – 1684), although his education in mathematics was probably not up to the French and British standards.

In 1666, at the age of 20, he published his habilitation thesis and first book, “De Arte Combinatoria” (“On the Art of Combinations”), in which he aimed to reduce all reasoning and discovery to a combination of basic elements (such as numbers, letters, sounds and colours). But, when the University of Leipzig refused to assure him a position teaching law upon graduation, he submitted it to the University of Altdorf instead, and obtained his doctorate in law there within five months. However, he then declined their offer of an academic appointment, and instead spent the rest of his life in the service of two major German noble families.

His first salaried position was as an alchemist in Nuremberg (even though he knew little or nothing about the subject). During this time, he met and was befriended by the wealthy Baron Johann Christian von Boineburg, who employed Leibniz as an assistant and later introduced him to the Elector of Mainz, Johann Philipp von Schönborn. The Elector asked Leibniz to assist with the redrafting of the legal codefor his Electorate and, in 1669, appointed him Assessor in the Court of Appeal. Although von Boineburg died late in 1672, Leibniz remained under the employment of his widow until she dismissed him in 1674.

Leibniz’s early service to the Elector was soon followed by a diplomatic role, and his political solution to the increasing ambitions of King Louis XIV of France (principally aimed at diverting him from attacking German areas) received cautious support in Germany and serious attention in France, although it was never actually implemented. However, during his time in Paris, from around 1672, he greatly expanded his knowledge of mathematics and physics, (especially after a stroke of luck in meeting the Dutch physicist and mathematician Christiaan Huygens, who became his mentor for a time), and began contributing to both, including the invention of his version of differential and integral calculus. He also met the leading French philosophers of the day, Nicolas Malebranche and Antoine Arnauld (1612 – 1694), and had the opportunity to study the published and unpublished writings of Descartes and Pascal.

After the French political plan petered out, the Elector of Mainz sent Leibniz on a similar peace mission to the English government in London, early in 1673. The mission ended abruptly with the news of the Elector’s death, but not before Leibniz had demonstrated to the Royal Society the first calculating machine that could execute all four basic arithmetical operations (a project he had been working on since 1670). He was made an external member of the prestigious Society, although he was criticized by some of the members, and the experience served to show him that his knowledge of mathematics was less than complete, and encouraged him to redouble his efforts.

With the sudden deaths of both the Elector of Mainz and (a few months earlier) of his other benefactor, von Boineburg, Leibniz returned to Paris, rather than Mainz. Duke Johann Friedrich (the Duke of Brunswick at that time), with whom Leibniz had been in correspondence since 1669, offered him the post of Councillorand librarian at his court in Hanover, and (with no apparent prospects in Paris or the Habsburg imperial court presenting themselves) he reluctantly accepted. He managed to delay his arrival in Hanover until the end of 1676, though, and in the meantime he travelled again to London (where he may have seen some of Sir Isaac Newton’s work on calculus, fuelling later claims that he had stolen ideas from Newton), and to The Hague in Holland, where he met Antonie van Leeuwenhoek(1632 – 1723), the discoverer of microorganisms. He also spent several days in intense discussion with the Dutch Rationalist philosopher, Baruch Spinoza, whom Leibniz greatly respected (although dismayed at his apparent contradiction of both Christian and Jewish orthodoxy).

In 1677, he was promoted to Privy Counsellor of Justice of the House of Hanover, a post he held for the rest of his life, serving three consecutive rulers as historian and political adviser, and as librarian of the ducal library. He was also correspondent, adviser and friend to several influential women in the Hanover court, including the Electress Sophia of Hanover, her daughter Sophia Charlotte of Hanover (the Queen of Prussia) and Caroline of Ansbach (consort of the future King George II of England) and, despite the rather provincial nature of Hanover itself, Leibniz was to some extent involved in European politics of the period.

He was also fortunate in that the Brunswicks allowed, and even encouraged, his intellectual pursuits unrelated to his duties as a courtier, as well as the vast correspondence he kept up. Assigned projects, like a commissioned history of the Guelf family of the House of Brunswick, however, often tended to take a back seat to his personal scientific and philosophical work, and his dilatoriness led to a certain amount of bad feeling.

Leibniz’s most important mathematical papers were published between 1682 and 1692, particularly in the “Acta Eruditorum”, a journal which he co-founded with Otto Mencke in 1682, and which played a key role in advancing his mathematical and scientific reputation. During the 1690s, he put much energy into promoting scientific societies, and he was involved in moves to set up academies in Berlin, Dresden, Vienna, and St. Petersburg. He was elected to the Paris Academy in 1701, after publication of his paper on the binary system of arithmetic. He kept up regular corrspondence with over 600 correspondents, including most of the great scholars of Europe, in a great variety of different fields. He often styled himself “von Leibniz”, even though we have no confirmation that he was ever granted a patent of nobility.

In 1712, Leibniz began a two year residence in Vienna, where he was appointed Imperial Court Councillor to the Habsburgs. When Elector Georg Ludwigbecame King George I of Great Britain in 1714, under the terms of the 1701 Act of Settlement (which Leibniz himself had done much to bring about), he had hoped to be brought into the British court, but his hopes were soon dashed (especially as Newton was seen as having “won” the calculus priority dispute). Finally, his dear friend and defender, the dowager Electress Sophia, died in 1714.

Leibniz himself died in Hanover, Germany, on 14 November 1716, and his funeral was shunned by the court of George I, the Royal Society and the Berlin Academy of Sciences, his grave remaining unmarked for more than 50 years. He had never married or raised a family, and he left a fair sum (earned from his well-paid position with the Brunswicks) to his sole heir, his sister’s stepson.


Leibniz wrote a great deal, but published hardly any of it during his life, his philosophy seeming to take a back seat to his many other interests and duties. Other than the “Théodicée” of 1710 (the only treatise Leibniz published in his lifetime), his philosophical writings consist mainly of a multitude of short pieces (journal articles, manuscripts published long after his death, and many letters to many correspondents), giving his philosophical thinking a fragmented appearance.

His first philosophical work, the “Discours de métaphysique” (“Discourse on Metaphysics”), written in 1686 but not actually published until the 19th Century, was a commentary on a running dispute between the French Rationalists Nicolas Malebranche and Antoine Arnauld (1612 – 1694), and led to an extensive and valuable correspondence with Arnauld (covering, among other matters, one of Leibniz’s lifelong aims, the reunification of the Christian Churches). Between 1695 and 1705, he wrote his “Nouveaux essais sur l’entendement humain”(“New Essays on Human Understanding”), a lengthy commentary on John Locke‘s 1690 “An Essay Concerning Human Understanding”, although it too was not published until 1765, long after his death.

The “Théodicée”, written in 1710, is as much theological as philosophical. It tries to justify the apparent imperfections of the world and to tackle the Problem of Evil in a world created by a good God by claiming that our world is optimal among all possible worlds, and that it must be the best possible and most balanced world, simply because it was created by a perfect God. The optimism of this idea was lampooned by Voltaire in his comic novella, “Candide”, although the modern observations that led to the “fine-tuned Universe” argument may seem to support his view.

Perhaps Leibniz’s best known contribution to Metaphysics (as exposited in the “Monadologie” of 1714), is his theory of monads, a form of dualistic Idealism sometimes known as Panpsychism or Parallelism. Monads are the ultimate elements of the universe: eternal, immaterial, indecomposable, individual, non-interacting, subject to their own laws, and each reflecting the entire universe in a pre-established harmony (effectively “programmed” in advance by God, whom he called the “central monad”, to “harmonize” with each other). Unlike atoms, monads possess no material or spatial character, and are completely mutually independent, so that interactions among monads are only apparent. For Leibniz, then, everything in the material world that we see and touch are actually only phenomena, merely appearances or by-products of the real world, which is in fact an infinite array of these non-material monads. In some ways, this is not unlike the very modern idea of the universe being ultimately composed of energy.

According to Leibniz’s theory, human beings and even God himself are monads, and the existence of God can be inferred from the harmony prevailing among all other monads (because it is God who wills the pre-established harmony). Thus, the external world is ideal (in the philosophical sense of Idealism) and phenomenal (in the philosophical sense of Phenomenology), and its motion is the result of a dynamic force (the pre-established harmony or, effectively, God) on these simple and immaterial monads. Although Leibniz claimed to believe in the existence of free will, his programme is essentially a deterministic one.

Leibniz also used his theory of monads in an attempt to overcome the problematic interaction between mind and matter arising in the system of Descartes (the so-called mind-body problem in Philosophy of Mind). Indeed, he developed the theory largely to address it, unimpressed as he was with Spinoza‘s earlier solution to this problem, with its lack of individuation and its representation of individual creatures as merely accidental. In Leibniz’s conception of things, there is really no need for the concept of causality at all, as everything is pre-arranged and organized by the omnipotent God himself. Leibniz’s theory was, however, considered somewhat arbitrary and eccentric, even in his own day.

Towards the end of his life, Leibniz published an essay called “Principles of Nature and Grace, Based on Reason” (1714), in which he put forth his Principle of Sufficient Reason, which states that there is an explanation for every fact and an answer to every question, however intractible they may appear. Following from this, he was perhaps the first philosopher to explicitly ask the question “Why is there something rather than nothing?”, a fundamental and apparently intractible question that others had shied away from. His answer to this question, perhaps disappointingly, was the rather formulaic one of God, and when asked for an explanation for God’s existence his equally unsatisfactory answer was that God is a necessary being, such that his non-existence would be logically impossible, a response that Hume and others took immediate issue with.

Although he published nothing on formal Logic in his lifetime, Leibniz can be considered the most important logician between Aristotle and the mid-19th Century developments in modern formal Logic of George Boole and Augustus De Morgan. He enunciated the principal properties of what we now call conjunction, disjunction, negation, identity, set inclusion and the empty set.

Quite early in his career, Leibniz’s developed a calculus ratiocinator, which resembles modern Symbolic Logic to some extent, based on his belief that much of human reasoning could be reduced to calculations of a sort, and out of his passion for symbols and notation. He defining a “real” character as a written sign that represents an idea directly, and not simply as the word embodying an idea (like Egyptian hieroglyphics, Chinese characters, and the symbols of astronomy and chemistry), and proposed a “universal characteristic”, built on an alphabet of human thought, in which each fundamental concept would be represented by a unique “real” character, with more complex thoughts represented by combining characters. Later, in 1676, when he had a better grounding in mathematics, he conceive of a kind of “algebra of thought”, modelled on and including conventional algebra and its notation.

In mathematics, Leibniz was the first (in 1692 and 1694) to employ the mathematical notion of a function explicitly to denote any of several geometric concepts derived from a curve, as well as the first to see that the coefficients of a system of linear equations could be arranged into an array (now called a matrix) which can be manipulated to find the solution of the system.

He is credited, along with Sir Isaac Newton, with the discovery of infinitesimal calculus, which, according to his notebooks, he employed for the first time in November 1675 to find the area under the function y = x. He introduced several notations used to this day (e.g. the elongated S for the integral sign, and the d used for differentials) and, in the autumn of 1676, he discovered the familiar d(xn) = nxn-1dx.

However, he did not publish anything about his calculus until 1684 and, from 1711 until his death, Leibniz’s life was envenomed by a long and antagonistic dispute with John Keill, Newton and others, over whether Leibniz had invented the calculus independently of Newton, or whether he had merely invented another notation for ideas that were fundamentally Newton’s. Although his approach to the calculus fell well short of later standards of rigour (as did Newton’s), and later work discredited the use of infinitesimals to justify calculus, his work marked an important startin the discipline, and much of his analysis has been vindicated.

As early as 1671, Leibniz began to invent a calculating machine, the first that could execute all four arithmetical operations, gradually improving it over a number of years (he was elected to the Royal Society in 1673 on the strength of it). By 1679, he had perfected his binary system of arithmetic (base 2), which was later used in most computers, although he did not publish anything until 1701. He imagined a machine in which binary numbers were represented by marbles, governed by a rudimentary sort of punched card system, groping towards hardware and software concepts worked out much later by Charles Babbage and Ada Lovelace.

In physics, Leibniz often disagreed with both Descartes and Newton. He devised a new theory of motion (dynamics) based on kinetic energy and potential energy, which posited space, time and motion as relative (whereas Newton felt strongly that space was absolute), anticipating by over 200 years Albert Einstein and recent cosmology and quantum mechanics. His “vis viva” (living force) represented an alternative viewpoint to the conservation of momentum championed by Newton in England and by Descartes in France.

He also dabbled in other sciences, often with prescient ideas. By proposing that the earth has a molten core, he anticipated modern geology. From his study of comparative anatomy and fossils, he worked out a primal organismic theory. In psychology, he anticipated the distinction between conscious and unconsciousstates, and in sociology, he laid the ground for communication theory. In public health, he advocated establishing a medical administrative authority, with powers over epidemiology and veterinary medicine. In economics, he proposed tax reforms and a national insurance scheme, and discussed the balance of trade.

He was also an inventor and engineer, and has been claimed as the “father of applied science”, insisting that theory be combined with practical application. He designed wind-driven propellers and water pumps, mining machines to extract ore, hydraulic presses, water desalination systems, lamps, submarines, clocks, etc, and (with Denis Papin) even an early steam engine.



Nicolas Malebranche (1638 – 1715)


220px-Nicolas_MalebrancheNicolas Malebranche (1638 – 1715) was a French philosopher of the Age of Reason. He was initially a follower of the Rationalism of René Descartes (or Cartesianism), and a vociferous opponent of the British Empiricist school of thought.

However, he was also a devout Christian, and sought to synthesize the thought of Descartes and St. Augustine in order to demonstrate the active role of God in every aspect of the world, developing in the process his own doctrine of Occasionalism.

He always enjoyed high esteem in his home country and, although his reputation outside France diminished during the 18th Century, many have begun to argue in recent years that the originality and unity of his philosophical system merits him a place alongside such Rationalist figures as Descartes, Spinoza and Leibniz.


Malebranche (pronounced mal-BRONSH) was born on 6 August 1638 in Paris, France, the youngest child of his father Nicolas Malebranche (a secretary to King Louis XIII of France) and his mother Catherine de Lauzon (the sister of a Viceroy of Canada).

He was born with a severely malformed spine and weak lungs, and he therefore received his early education from a private tutor. However, he left home at the age of sixteen to study at the University of Paris, first at the Collège de la Marche where he pursued a course of philosophy, and subsequently at the Collège de Sorbonnewhere he studied theology. He rejected the Scholasticism taught at the university, though, and entered the Paris Oratory in 1660, where he devoted himself to ecclesiastical history, linguistics, the Bible, and the works of St. Augustine. He was ordained a priest in 1664.

It was also in 1664, that Malebranche happened upon Descartes’ “Traité de l’homme” (“Treatise on Man”), an account of the physiology of the human body without resorting to Aristotelianism and Scholasticism. He was so impressed with the work, and the possibilities it suggested, that he spent the next decade studying Descartes’s system in detail.

At the end of that time, in 1674 and 1675, Malebranche published the two volumes of his first and most extensive philosophical work, “De la recherche de la vérité”(“Concerning the Search after Truth”), which laid the foundations for his philosophical reputation and ideas. In later editions, he responded to criticismsand substantially expanded on the original arguments. Gottfried Leibniz met Malebranche in Paris in about 1675, and the two corresponded at length thereafter.

Malebranche published his “Traité de la nature at de la grâce” (“Treatise on Nature and Grace”) in 1680, and the attacks on it by fellow Cartesian philosopher (and Jansenist), Antoine Arnauld (1612 – 1694), led to a long and bitter dispute, mainly on theological grounds, but which also branched out into most areas of their respective philosophical systems. Arnauld’s supporters persuaded the Roman Catholic Church to place the “Treatise on Nature and Grace” on its Index of Prohibited Books in 1690 (and “Concerning the Search after Truth” was also prohibited later, in 1709).

Malebranche continued to publish books throughout the 1680s, and he died in Paris on 13 October 1715 at the age of 77.


Like René Descartes, Malebranche held that humans attain knowledge through ideasor immaterial representations in the mind, but whereas Descartes believed that ideas were mental entities, Malebranche argued (more or less following St. Augustine) that all ideas exist only in God and that we see all things in God (“vision in God”). These ideas, therefore, are uncreated and independent of finite minds and, when we access them intellectually, we apprehend objective truth.

Malebranche divided truth (which he saw in terms of relations between ideas) into two categories: relations of magnitude (“speculative” truths, such as those of geometry) and relations of quality or perfection (the “practical” truths of ethical principles which, for Malebranche, were divine in their foundation, universal in their application, and to be discovered by intellectual contemplation).

His great innovation was to explain how universal divine ideas could also serve as the immediate objects of human minds in the sensual perception of particulars, by suggesting that, whereas the mind’s intellectual conception of ideas is pure and direct, its sensual perception of them will be modified by “sensations” proper to individual created minds. Thus, to a different mind (one with a different sensation), the same idea could represent a different individual of the same general kind.

Malebranche’s initial approach to the mind-body problem followed of the Dualism of Descartes, but later, in the “Entretiens sur la métaphysique et la religion(“Dialogues on Metaphysics and Religion”) of 1688 for example, he argued that we do not have a complete conception of the powers of the mind, and thus no clear conception of the nature of the mind. With regard to psycho-physical interaction, Malebranche argued that body could not act on mind, nor mind on body, and the only active power (and the only efficient cause of change in the world) is God.

This idea developed into Malebranche’s main doctrine of Occasionalism, that God is the only causal agent and that all created things merely provide “occasions” for divine activity. For example, God’s laws governing what we call the “interaction”of body and mind, are such that similar movements in the body will “occasion” similar ideas in the mind, although in reality both the idea in the mind and the movement in the body are caused by God.

He also held that, in creating the world, God observed what Malebranche called “order” and bound himself to act according to a few simple laws of nature, chosen in accordance with his general will that the world be as good as possible. He used this idea of general will or volition in his theodicy (his reponse to the fact of the the existence of evil in a world created by a good God), arguing that, although God could act by particular volitions to prevent specific natural evils, he could only do so by departing from the simple laws of his general volitions, which are the supreme mark of His wisdom. Thus, for the most part, God acts through “general volitions” only (which may necessitate some specific evils), and it is only in exceptional cases (e.g. miracles) that he would resort to “particular volitions”.

Malebranche’s ideas greatly influenced the theory of Immaterialism or Pure Idealism of Bishop George Berkeley and, entirely independently of him, Arthur Collier (1680 – 1732), as they took the final step to a full denial of the existence of material substance. Gottfried Leibniz was also inspired by his correspondence with Malebranche to design his theory of pre-established harmony as an alternative to Malebranche’s Occasionalism. David Hume drew upon Malebranche’s negative arguments to show that no genuine causal connections could be conceived between distinct entities, although Hume then turned inwards to the workings of the human mind for his solutions, rather than upwards to God.

In addition to his major works on Metaphysics, Philosophy of Mind, theology and Ethics, Malebranche also published studies of optics, the laws of motion and the nature of colour, and he particularly pursued such non-philosophical areas late in life. He also wrote on mathematics and, although he made no major mathematical discoveries of his own, he was instrumental in introducing and disseminating the contributions of Descartes and Leibniz in France.

John Locke (1632 – 1704)


lockeJohn Locke (1632 – 1704) was an English philosopher of the Age of Reason and early Age of Enlightenment. His ideas had enormous influence on the development of Epistemology and Political Philosophy, and he is widely regarded as one of the most influential early Enlightenment thinkers.

He is usually considered the first of the British Empiricists, the movement which included George Berkeley and David Hume, and which provided the main opposition to the 17th Century Continental Rationalists. He argued that all of our ideas are ultimately derived from experience, and the knowledge of which we are capable is therefore severely limited in its scope and certainty.

His Philosophy of Mind is often cited as the origin for modern conceptions of identity and “the self”. He also postulated, contrary to Cartesian and Christian philosophy, that the mind was a “tabula rasa” (or “blank slate”) and that people are born without innate ideas.

Along with Thomas Hobbes and Jean-Jacques Rousseau, he was also one of the originators of Contractarianism (or Social Contract Theory), which formed the theoretical groundwork of democracy, republicanism and modern Liberalism and Libertarianism. He is sometimes referred to as the “Philosopher of Freedom”, and his political views influenced both the American and French Revolutions.


Locke was born on 29 August 1632 in the small rural village of Wrington, Somerset, England. His father, also named John Locke, was a country lawyer and clerk to the Justices of the Peace in nearby town of Chew Magna, and had served as a captain of cavalry for the Parliamentarian forces during the early part of the English Civil War. His mother, Agnes Keene, was a tanner’s daughter and reputed to be very beautiful. Both parents were Puritans, and the family moved soon after Locke’s birth to the small market town of Pensford, near Bristol.

In 1647, Locke was sent to the prestigious Westminster School in London (sponsored by the local MP Alexander Popham) as a King’s Scholar. After completing his studies there, he was admitted to Christ Church, Oxford. Although a capable student, Locke was irritated by the largely classical (Aristotelian) undergraduate curriculum of the time, and found more interest in the works of modern philosophers such as René Descartes, and the more experimental philosophy being pursued at other universities and within the embryonic Royal Society.

Locke was awarded a bachelor’s degree in 1656, and a master’s degree in 1658. He was elected lecturer in Greek in 1660 and then in Rhetoric in 1663, but he declined the offer of a permanent academic position in order to avoid committing himself to a religious order. During his time at Oxford, he also studied medicineextensively, and worked with such noted scientists and thinkers as Robert Boyle, Thomas Willis, Robert Hooke and his friend from Westminster School, Richard Lower. He later obtained a bachelor of medicine qualification in 1674.

It was through his medical knowledge that he obtained the patronage of the controversial political figure, Lord Anthony Ashley Cooper (the 1st Earl of Shaftesbury), and in 1667 he moved to Shaftesbury’s London home to serve as his personal physician. He was credited with saving Shaftesbury’s life afer a liver infection became life-threatening. In London, Locke continued his medical studies under the tutelage of Thomas Sydenham, who also had a major influence on Locke’s natural philosophical thinking.

During the 1670s, Locke served as Secretary of the Board of Trade and Plantations and Secretary to the Lords and Proprietors of the Carolinas, helping to shape his ideas on international trade and economics. Locke became more involved in politics (and further developed his political ideas) when Shaftesbury, a founder of the Whig movement in British politics, became Lord Chancellor in 1672. It was also during this time in London that he worked on early drafts of his “An Essay Concerning Human Understanding”, eventually published in 1690 and considered one of the principal sources of Empiricism in modern philosophy.

After some time travelling across France following Shaftesbury’s fall from favour in 1675, he returned to England in 1679 (when Shaftesbury’s political fortunes took a brief positive turn), and began the composition of his famous work of Political Philosophy, the “Two Treatises of Government”, which was published anonymously (in order to avoid controversy) in 1689, and whose ideas about natural rights and government were quite revolutionary for that period in English history.

In 1683, Locke fled to Holland, under strong (but probably unfounded) suspicion of involvement in the Rye House Plot. He did not return to England until 1688’s Glorious Revolution and the overthrow of King James II by the of the Dutchman William of Orange (King William III of England), which Locke saw as the ultimate triumph of his revolutionary cause. The publication of “An Essay Concerning Human Understanding”, the “Two Treatises of Civil Government” and “A Letter Concerning Toleration” all occurred in quick succession upon his return from exile. His “Essay” in particular brought great fame, and Locke spent much of the rest of his life responding to admirers and critics by making revisions in later editions of the book.

In 1691, he moved to his close friend Lady Masham’s country house at Oates, Essex. During this period, he became something of an intellectual hero of the Whigs, and he discussed matters with such figures as John Dryden and Sir Isaac Newton. He continued to work at the Board of Trade from 1696 until his retirement in 1700.

However, his health deteriorated, marked by regular asthma attacks, and he died on 28 October 1704, and was buried in the churchyard of High Laver. He never married, and had no children.


Locke wrote on philosophical, scientific and political matters throughout his life, in a voluminous correspondence and ample journals, but the public works for which he is best known were published in a single, sudden burst in 1689 – 1690.

The fundamental principles of Locke’s Epistemology are presented in his monumental “An Essay Concerning Human Understanding” of 1690, the culmination of twenty years of reflection on the origins of human knowledge. In it he argued the empiricist approach that would be adopted by the British Empiricism movement: that all of our ideas, whether simple or complex, are ultimately derived from experience and sensory input. The knowledge of which we are capable is therefore severely limited in its scope and certainty, in that we can never know the inner nature of the things around us, only their behaviour and the way in which they affect us and other things (a kind of modified Skepticism). One of the ways in which they affect us is through our senses, giving us experiences (or representations or images) of their properties or qualities.

Locke saw the properties of things as being of two distinct kinds. Their real inner natures derive from the primary qualities, which we can never experience and so never know. Our knowledge of material substances, therefore, depends heavily on their secondary qualities (by reference to which we also name them), which are mind-dependent and of a sensory or qualitative nature. He therefore believed in a type of Representationalism, that these primary qualities are “explanatorily basic” in that they can be referred to as the explanation for other qualities or phenomena without requiring explanation themselves, and that these qualities are distinct in that our sensory experience of them resembles them in reality.

He claimed that “the mind is furnished with ideas by experience alone” (an idea being something within the mind that represents things outside the mind). However, he also argued that a proper application of our cognitive capacities is enough to guide our action in the practical conduct of life, and that it is in the process of reasoning that the mind confronts the raw ideas it has received (an approach not dissimilar to the Dualism of Descartes). His definition of knowledge might be stated, then, as the perception of the relationship between ideas.

Where Locke differed markedly from Descartes and other predecessors, though, was in the status he granted to the senses. Descartes held that the senses incline us to have certain beliefs, but that this alone does not amount to actual knowledge (which requires interpretation and explanation by reason and the intellect). For Locke, however, the senses themselves are a basic and fundamental faculty which deliver knowledge in their own right. Indeed, his whole conception of an idea differed from that of Descartes: for Descartes, an idea was fundamentally intellectual; for Locke it was fundamentally sensory, and all thought involved images of a sensory nature.

In later editions of the treatise, he also included detailed accounts of human volition and moral freedom, the personal identity on which our responsibility as moral agents depends, and the dangers of religious enthusiasm.

With his “Two Treatises of Civil Government”, published anonymously in 1690 in order to avoid controversy, Locke established himself as a political theorist of the highest order. The “First Treatise” was intended merely to refute Sir Robert Filmer’s support of the Divine Right of Kings, arguing that neither scripture nor reason supports Filmer’s contentions. The “Second Treatise”, however, offered a systematic account of the foundations of political obligation. In Locke’s view, all rights begin in the individual property interest created by an investment of labour. The social structure (or “commonwealth”) depends for its formation and maintenance on the express consent of those governed by its political powers (the so-called Social Contract or Contractarianism). He believed that majority rulethus becomes the cornerstone of all political order, although dissatisfied citizensreserve a lasting right to revolution.

Like Thomas Hobbes before him, Locke started from a belief that humans have absolute natural rights, in the sense of universal rights that are inherent in the nature of Ethics, and not contingent on human actions or beliefs (a kind of Deontology). However, much of his political work is characterized by his opposition to authoritarianism, and particularly to the tendency towards Totalitarianism advocated by Hobbes. Locke believed that no one should be allowed absolute power, and introduced the idea of the separation of powers, whereby the Church and the judicial system operate independently of the ruling class. In particular, he defined our civil interests (those which the State can and should legitimately protect) as life, liberty, health and property, specifically excluding religious concerns, which he saw as outside the legitimate concern of civil government. If much of this seems familiar from the American Declaration of Independence, that is no coincidence as the American founding fathers freely admitted their debt to Locke’s Political Philosophy.

His “Letter Concerning Toleration” of 1689 came in the wake of King Louis XIV of France’s revocation of the Edict of Nantes (and the religious persecutionwhich followed it). It argued for a broad (though not limitless) acceptance of alternative religious convictions, as well as a strict separation betwen Church and State. In his 1695 “The Reasonableness of Christianity”, he argued that the basic doctrines of Christianity are relatively few and entirely compatible with reason.

In 1693, Locke produced his contribution to the Philosophy of Education, his influential “Some Thoughts Concerning Education”. In it, he claimed (influenced by Avicenna and the Medieval Avicennist movement) that a child’s mind is a tabula rasa (or blank slate) and does not contain any innate ideas, nor anything that might be described as human nature. Thus, all men are created equal, and each of us can be said to be the author of our own character. These ideas flowed logically and seamlessly from Locke’s underlying belief in Empiricism, that all human knowledge derives from the senses and that therefore there can be no knowledge that precedes observation.

According to Locke, the mind was to be educated by a three-pronged approach: the development of a healthy body; the formation of a virtuous character; and the choice of an appropriate academic curriculum. He maintained that a person is to a large extent a product of his education, and also pointed out that knowledge and attitudes acquired in a child’s early formative years are disproportionately influential and have important and lasting consequences.

Baruch Spinoza (1623 – 1677)


SpinozaBaruch Spinoza (AKA Benedict Spinoza) (1623 – 1677) was a Dutch philosopher of Portuguese Jewish origin who lived and worked during the Age of Reason.

Along with René Descartes and Gottfried Leibniz, he is considered one of the great Rationalists of the 17th Century, although the breadth and importance of his work was not fully realized until years after his death.

An enormously controversial figure (both in his own day and after) for the highly original and provocative positions he advocated, Spinoza is nowadays respected as one of the definitive ethicists (he took a largely Moral Relativist position), and as a harbinger of enlightened modernity. His metaphysical views were essentially monistic and pantheistic, holding that God and Nature were just two names for the same single underlying reality.


Spinoza was born on 24 November 1632 in Amsterdam, Holland, to a family of Sephardic Jews descended from displaced Maranos from Portugal. His father was Abraão (Miguel) de Spinoza, a successful importer and merchant; his mother was Ana Débora, Miguel’s second of three wives, who died when Baruch was only six years old.

He had a traditional Jewish upbringing, and his early education consisted mainly of religious study, including instruction in Hebrew, liturgy, Torah, prophetic writings and rabbinical commentaries. However, his critical, curious nature would soon come into conflict with the Jewish community.

At the age of 17, when his father died in the wars against England and France and the family fortune was decimated, Spinoza was forced to cut short his formal studies to help run the family business, although he was eventually able to relinquish responsibility for the business and its debts to his brother, Gabriel, and devote himself to his real love, philosophy. He gave away his share of his father’s inheritance to his sister, and lived the rest of his life in genteel poverty as a grinder of optical lenses.

In 1656, Spinoza was issued a writ of “cherem” (the Jewish equivalent of excommunication) for the apostasy of how he conceived God, and for various positions contrary to normative Jewish belief and his criticisms of the Talmudand other religious texts. He had reportedly been offered 1000 florins to keep quietabout his views, but had refused on principle. Following his excommunication, he adopted the first name Benedictus or Benedict (the Latin equivalent of Baruch, meaning “blessed”) or, more informally, the Portuguese equivalent Bento.

After his excommunication, Spinoza lived and worked at times at the school of his old Latin teacher, Franciscus van den Enden, an atheist and devotee of the Rationalism of Descartes, who was forbidden by the city government to propagate his doctrines publicly. He dedicated himself completely to philosophy, and his fervent desire was to change the world through establishing a clandestine philosophical sect, although this was only eventually realized after his death, through the dedicated intercession of his friends.

He became acquainted with several Collegiants, members of an eclectic sect with tendencies towards Rationalism, as well as corresponding with Petrus Serrarius(1600 -1669), a radical Protestant and millennarian merchant, who acted as a patron of Spinoza for a time. By the beginning of the 1660s, Spinoza’s name had become more widely known, and he met and corresponded with Gottfried Leibniz and Henry Oldenburg (1619 – 1677). Around 1661, he relocated from Amsterdam to Rijnsburg (near Leiden) and later lived in Voorburg (1663) and then The Hague, earning a comfortable living from his work as an optician and lens-grinding, although he was also supported by small, but regular, donations from close friends. He never married, nor did he father any children.

Spinoza’s first publication was a geometric exposition of the work of Descartes, the two part “Principia philosophiae cartesianae” (“Principles of Cartesian Philosophy”), published in 1663. In the early 1660s, he worked on what was to become his magnum opus, the “Ethics”, but he suspended the work in 1665 in favour of his “Tractatus Theologico-Politicus” (“Theologico-Political Treatise”), which was eventually published anonymously in 1670. The public reaction to this work, though, was extremely unfavourable and Spinoza was wary enough to abstain from publishing more of his works for the rest of his life (the “Ethics” and several other works were all published posthumously by his friends, in secrecy). Even his colleague Leibniz disagreed harshly with it (and published his own detailed refutation), although some of Leibniz’s own work bears some striking resemblances to certain key parts of Spinoza’s philosophy. In 1676, Spinoza met with Leibniz at The Hague to privately discuss his “Ethics”, which he had just completedbut dared not publish.

Spinoza died at the young age of 44 on 21 February 1677 in The Hague, due to a lung illness (perhaps tuberculosis or silicosis, possibly due to breathing in fine glass dust from the lenses he ground). Even after his death, Spinoza did not escape controversy, and in 1678 his works were banned throughout Holland.


Although he is usually counted, along with Descartes and Leibniz, as one of the three major Rationalists of the 17th Century, his writings reveal the influence of such divergent sources as Stoicism, Jewish Rationalism, MachiavelliHobbes, Descartes and a variety of heterodox religious thinkers of his day, and he made significant contributions in virtually every area of philosophy. His pursuits were eclectic and his thought was strikingly original, which makes him somewhat difficult to categorize.

His first published work, the “Principia philosophiae cartesianae”(“Principles of Cartesian Philosophy”) of 1663, was a systematic presentation of the philosophy of Descartes, to which he added his own suggestions for its improvement, and it already contained many of the characteristic elements of his later work. The “Tractatus Theologico-Politicus”(“Theologico-Political Treatise”) of 1670 was an examination of superficial popular religion in general and a vigorous critique of the militant Protestantismpractised in Holland at the time. He argued that Christians and Jews could live peaceably together if they would only rise above the petty theological and cultural controversies that divided them. The core of Spinoza’s ethical views was encapsulated in his early “Tractatus de intellectus emendatione” (“Treatise on the Improvement of the Understanding”).

But his major work was the monumental “Ethica Ordine Geometrico Demonstrata” (“Ethics”), an abstract and difficult work, finished in 1676 but only published posthumously in 1677. Each of its five consituent books comprises a long sequence of numbered propositions, each of which is deduced through a method consciously modelled on the deductive logic used by the Greek mathematician Euclidin his seminal work on geometry. Like Euclid, Spinoza started with a small set of self-evident definitions and axioms, meticulously built up his deductive argument, and concluded each section with a triumphant “QED” (“quod erat demonstrandum”, or “that which was to be demonstrated”). It is sometimes held up as a supreme example of a self-contained metaphysical system, whose object is nothing less than to explain everything, the total scheme of reality.

As a young man, Spinoza had subscribed to Descartes’ belief in Dualism, that body and mind are two separate substances. However, he later changed his view (as demonstrated in the “Ethics”) and asserted that they were not separate, but a single identity, and that body and mind were just two names for the same reality. Starting from Descartes’ definition of substance as “that which requires nothing other than itself in order to exist”, Spinoza’s conclusion was quite different from that of Descartes: where Descartes saw the one underlying substance as being God, Spinoza saw it as the totality of everything (in other words, Nature). All of reality, then, was really just one substance, and all apparently different objects were merely facets or aspects (what he called “modes”) of that underlying substance. In this way, Spinoza refined Descartes’ rather unsatisfactory treatment of the mind-body problem in Philosophy of Mind by positing that the physical and mental worlds (extension and consciousness) were essentially one and the same thing. This was therefore a kind of Monism, as opposed to Descartes’ Dualism, (more specifically, it was a historically significant solution known as Neutral Monism).

Following on from this analysis, then, Spinoza saw God and Nature as just two names for the same reality of the universe, essentially a kind of Pantheism. Thus, he believed that there was just one set of rules governing the whole of reality, and that the basis of the universe was a single substance, of which all lesser entities are actually “modes” or modifications. Spinoza’s “God” (or “Nature”) was therefore a being of infinitely many attributes, of which extension and thought were but the two that we can understand. He envisaged a God that was not a transcendent creator of the universe who rules over the universe by providence, but a God that itself is the deterministic system of which everything in nature is a part. Thus, for Spinoza, God effectively is the infinite natural world and He has no separate “personality”, nor is he in some way outside of Nature (supernatural).

Spinoza was a thoroughgoing determinist who held that absolutely everything that happens occurs through the operation of necessity, leaving absolutely no room for free will and spontaneity. For him, even human behaviour is fully determined, and freedom (or what we presume to be free will) is limited to merely our capacity to know that we are determined and to understand why we act as we do. Nothing happens by chance in Spinoza’s world, and reason does not work in terms of contingency.

Spinoza’s Ethics have much in common with Stoicism in as much as both philosophies sought to fulfill a therapeutic role by instructing people how to attain happiness(Eudaimonism). He asserted that the “highest good” was knowledge of God, which was capable of bringing freedom from fear and the tyranny of the passions, and ultimately true blessedness. However, Spinoza differed sharply from the Stoics in his rejection of their contention that reason could overcome emotion. He contended that an emotion can only be displaced or overcome by a stronger emotion, and that knowledge of the true causes of passive emotions (those not rationally understood) could transform them into active emotions (ones that can be rationally understood), thus anticipating by over 200 years one of the key ideas of the psychoanalysis of Sigmund Freud (1856 – 1939).

Spinoza took the Moral Relativist position that nothing is intrinsically good or bad, except to the extent that it is subjectively perceived to be by the individual. In a completely ordered world where “necessity” reigns, the concepts of Good and Evilcan have no absolute meaning. Everything that happens comes from the essential nature of objects or of God/Nature, and so, according to Spinoza, reality is perfection, and everything done by humans and other animals is also excellent and divine. If circumstances sometimes appear unfortunate or less than perfect to us, it is only because of our inadequate conception of reality. He asserted that sense perception, though practical and useful for rhetoric, is inadequate for discovering universal truth.

While it is easy to see why both the Jewish and Christian authorities of Spinoza’s day felt both appalled and threatened by his ideas, his philosophy did hold an attraction for late 18th Century Europeans in that it provided an alternative to Materialism, Atheism and Deism. Three of Spinoza’s ideas in particular strongly appealed to them: the unity of all that exists; the regularity and order of all that happens; and the identity of spirit and nature.

Blaise Pascal (1623 – 1662)


blaise pascalBlaise Pascal (1623 – 1662) was a French philosopher, mathematician and scientist of the Age of Reason.

His earliest (and best known) work was as a mathematicianof the first order, especially in the areas of projective geometry and probability theory, and he made important contributions to the natural and applied sciences and wrote in defence of the scientific method. He is also regarded as one of the most important authors of the French Classical Period and one of the greatest masters of French prose.

After a mystical experience late in his short life, however, he devoted himself to philosophy and theology. He opposed both the Rationalism of René Descartes and the main countervailing philosophy, British Empiricist, as being insufficient for determining major truths.


Pascal was born on 19 June 1623 in Clermont-Ferrand in central France. His father was Étienne Pascal, a local judge and aristocrat, who also had an interest in science and mathematics; his mother was Antoinette Bégon, who died when Pascal was just three years old. He had two sisters, the younger Jacqueline and the elder Gilberte. In 1631, his father sold his legal position (a common practice in that time) and invested the money in a government bond which provided a comfortable (if not a lavish) income, and which allowed the family to move to Paris. There, they hired Louise Delfault as a maid, and she eventually became an instrumental member of the family (although his father never remarried).

Pascal’s father decided to educate his children himself, for they all showed extraordinary intellectual ability, particularly his son Blaise who was clearly something of a child prodigy. He taught his son grammar, Latin, Spanish, and mathematics, all according to an original method. The young Pascal showed an amazing aptitude for mathematics and science, composing a treatise on the sounds of vibrating bodies at age eleven, and an independent proof of the sum of the angles of a triangle at twelve.

The boy was then allowed to study Euclid, and to sit in (as a silent on-looker) at the gatherings at the monastic cell of Père Marin Mersenne (1588 – 1648), where some of the greatest mathematicians and scientists in Europe (including Gilles de Roberval, Gérard Desargues, Claude Mydorge, Pierre Gassendi and René Descartes) often met. As a result of this, the precocious sixteen year old Pascal submitted to the group a treatise on the geometry of cones, which included what has come to be known as Pascal’s Theorem.

In 1638, however, Cardinal Richelieu defaulted on the government’s bonds (in order to fund his war efforts), and the Pascal family found themselves in much reduced circumstances. His father was eventually forced to flee Paris because of his opposition to Richelieu’s fiscal policies, and the children were left for a while in the care of their neighbour Madame Sainctot (a great beauty with an infamous past, who kept one of the most glittering and intellectual salons in all France). By the following year, however, Pascals’ father had been restored to the Cardinal’s good graces, and even appointed as the king’s commissioner of taxes in the city of Rouen.

From as early as his eighteenth year, Pascal suffered from a nervous ailment that left him hardly a day without pain. Nevertheless, throughout the 1640s and early 1650s, Pascal produced some of his most famous mathematical work (including what have become known as Pascal’s Calculator and Pascal’s Triangle, and work on the theory of probabilities and the calculus of probabilities), and scientific work (particularly in the fields of hydrodynamics and hydrostatics, and including the inventions of the hydraulic press, the syringe, and a much improved barometer).

In 1647, a paralytic attack so disabled him that he moved to Paris with his sister Jacqueline in search of better medical treatment. His health improved a little, but his nervous system had been permanently damaged and he was subject to deepening hypochondria and fits of anger and depression.

Around this time, he also became interested in the teachings of a Catholic splinter group known as Jansenism, which was becoming popular in France at the time, and he began to write on theological subjects for the first time in the course of 1647, although this initial religious engagement soon faded. His father died in 1651, leaving his inheritance to Pascal and Jacqueline, who then left to become a postulant in the Jansenist convent of Port-Royal.

In November 1654, he had a brush with death after a carriage accident, from which he emerged unscathed but the shock of which apparently led to an intense religious vision which revitalized his belief and religious commitment. He started regularly visiting the convents at Port-Royal for retreats and began writing his first major literary work on religion, the “Lettres provinciales” (“Provincial Letters”). His religion was reinforced by an apparent miracle at Port-Royal, and he set his mind to write his final, unfinished testament (and most influential theological work), the “Pensées” (“Thoughts”), now widely considered to be his masterpiece and a landmark in French prose.

In his latter years in Paris, he followed an ascetic lifestyle and, in 1659, Pascal, whose health had never been good, fell seriously ill, rejecting the ministrations of his doctors in the belief that “sickness is the natural state of Christians”. King Louis XIV suppressed the Jansenist movement in 1661, and his sister Jacqueline died the same year, leading Pascal to relax his religious fervour somewhat. In 1662, Pascal’s illness became more violent, and he eventually died after suffering convulsions on 19 August 1662, just 39 years old.


Pascals’s philosophical and theological writing began only late in life, after his mystical religious vision of 1654. His first major literary work on religion, the “Lettres provinciales” (“Provincial Letters”), was published between 1656 and 1657 under a pseudonym. It attacked the casuistry (case-based, as opposed to principle-based, reasoning) of many Catholic thinkers in the early modern period (especially the Jesuits) as the mere use of complex reasoning to justify moral laxity and all sorts of sins. It provoked and incensed both King Louis XIV (who ordered the books shredded and burnt), and Pope Alexander VII (who condemned them, despite being persuaded by Pascal’s arguments). However, the “Provincial Letters” were extremely popular as a literary work, and influenced the prose of later French writers like Voltaire and Jean-Jacques Rousseau.

Pascal’s most influential theological work, referred to posthumously as the “Pensées”(“Thoughts”) although originally entitled “Apologie de la religion Chrétienne”(“Defence of the Christian Religion”), was not completed before his death. On its first publication in 1670 (albeit expurgated for the times) it instantly became a classic, and is widely considered Pascals’ masterpiece as well as a landmark in French prose. It was to have been a sustained and coherent examination and defence of the Christian faith, although it never quite lived up to that. One of its (high risk) main strategies was to use the contradictory philosophies of Skepticism and Stoicism (exemplified by Michel de Montaigne and Epictetus respectively) in order to bring the unbeliever to such despair and confusion that he would embrace God. It confirmed Pascal’s position as a Fideist (the view that religious beliefdepends on faith or revelation, rather than reason, intellect or natural theology.

Pascal’s best kown foray into the Philosophy of Religion was his argument for belief in God, which has become known as Pascal’s Wager. It is based not on an appeal to evidence that God exists, but rather that it is in our interests to believe in God and it is therefore rational for us to do so. He argued as follows: If we believe in God, then if he exists we will receive an infinite reward in heaven, while if he does not then we have lost little or nothing. Conversely, if we do not believe in God, then if he existswe will receive an infinite punishment in hell, while if he does not then we will have gained little or nothing. Thus, “either receiving an infinite reward in heaven or losing little or nothing” is clearly preferable to “either receiving an infinite punishment in hell or gaining little or nothing”, so it is rational to believe in God, even if there is no evidence that he exists.

As a young man, Pascal had already proved himself a mathematician of the first order, writing his first mathematical treatises as young as 11 or 12 years old. In 1642 (then not yet nineteen), he constructed a mechanical calculator capable of addition and subtraction, known as Pascal’s Calculator (or the Pascaline), the first and most basic of around fifty he built over the course of his life. In 1653, he completed another mathematical milestone, his “Traité du triangle arithmétique”(“Treatise on the Arithmetical Triangle”) in which he described a convenient tabular presentation for binomial coefficients, now called Pascal’s Triangle. In 1654, he corresponded with Pierre de Fermat (1601 – 1665) on the new mathematical theory of probabilities, and their work on the calculus of probabilities laid important groundwork for Gottfried Leibniz’s later formulation of the infinitesimal calculus.

In the late 1640s and early 1650s, Pascal pursued the study of hydrodynamics and hydrostatics, and clarified the concepts of pressure and vacuum (the possibility of which had been denied since Aristotelian times) by generalizing the early work of Evangelista Torricelli (1608 – 1647) on barometers, which he first encountered in 1646. His inventions include the hydraulic press (using hydraulic pressure to multiply force) and the syringe.

He also gave one of the 17th Century’s major statements on the scientific method: “In order to show that a hypothesis is evident, it does not suffice that all the phenomena follow from it; instead, if it leads to something contrary to a single one of the phenomena, that suffices to establish its falsity”.

René Descartes (1596 – 1650)


rene-descartesRené Descartes (1596 – 1650) was a French philosopher, mathematician, scientist and writer of the Age of Reason. He has been called the “Father of Modern Philosophy”, and much of subsequent Western philosophy can be seen as a response to his writings. He is responsible for one of the best-known quotations in philosophy: “Cogito, ergo sum” (“I think, therefore I am”).

He was a pioneer and major figure in 17th Century Continental Rationalism (often known as Cartesianism) later advocated by Baruch Spinoza and Gottfried Leibniz, and opposed by the British Empiricist school of thought of Hobbes, Locke, Berkeley and Hume. He represents a major break with the Aristotelianism and Scholasticism of the Medieval period.

His contribution to mathematics was also of the first order, as the inventor of the Cartesian coordinate system and the founder of analytic geometry, crucial to the invention of calculus and mathematical analysis. He was also one of the key figures in the scientific revolution of the 16th and 17th Centuries.


Descartes (pronounced day-CART) was born in the town of La Haye en Touraine(since renamed Descartes) in the Loire Valley in central France on 31 March 1596. His father, Joachim Descartes, was a busy lawyer and magistrate in the High Court of Justice, and his mother, Jeanne (née Brochard), died of tuberculosis when René was just one year old. René and his brother and sister, Pierre and Jeanne, were therefore mainly raised by their grandmother.

From 1604 until 1612, he attended the Jesuit Collège Royal Henry-Le-Grand at La Flèche, Anjou, studying classics, logic and traditional Aristotelianism philosophy. His health was poor and he was granted permission to remain in bed until 11 o’clock in the morning, a custom he maintained for the rest of his life. He then spent some time in Paris studying mathematics, before studing law at the University of Poitiers, in accordance with his father’s wishes that he should become a lawyer, obtaining his law degree in 1616.

However, he then abandoned his education and spent several years travelling and experiencing the world (he later claimed that his formal education provided little of substance). It was during this time (in 1618) that he met the Dutch philosopher and scientist Isaac Beeckman (1588 – 1637) while walking through Breda in Holland, who sparked his interest in mathematics and the new physics.

In 1622, he returned to France, and soon afterwards sold all his property at La Haye, investing the proceeds in bonds which provided him with a comfortable income for the rest of his life. He returned to settle in Holland in 1628. The next year, he joined the University of Franeker; the year after that, Leiden University; and, in 1635, he is recorded as attending Utrecht University. He had a daughter, Francine, after a relationship in Amsterdam with a servant girl, Helène Jans, although Francine died at the age of fve. In fact, in the years between 1828 and 1649, he lived at 14 separate addresses in 10 different Dutch cities.

It was during this 20 year period of frequent moves that he wrote almost all of his major works on philosophy, mathematics and science. He shrewdly held off publication of his first work, “Le Monde” (“The World”), written between 1629 and 1633, due to the condemnation of the works of Galileo Galilei (1564 – 1642) and Nicolaus Copernicus (1473 – 1543) by the Roman Catholic Church in 1633. The most famous of his works include: the “Discours de la méthode pour bien conduire sa Raison et chercher la Vérité dans les Sciences” (“Discourse on the Method”) of 1637, his first rationalist vision of the progress of human knowledge; the “Meditationes de Prima Philosophia” (“Meditations on First Philosophy”) of 1641, a more formal exposition of his central tenets, in Latin; and the “Principia Philosophiae” (“Principles of Philosophy”) of 1644, an even more systematic and comprehensive exposition of his views. For a time, in 1643, Cartesian philosophy was condemned by the University of Utrecht.

Descartes died of pneumonia on 11 February 1650 in Stockholm, Sweden, where he had been invited as a teacher for Queen Christina of Sweden. Later, his remains were taken to France and buried in the church of Sainte-Geneviève-du-Mont in Paris, and then, during the French Revolution, disinterred for burial in the Panthéon among the other great thinkers of France. Currently, his tomb is in the church of Saint-Germain-des-Prés in Paris, and his brain is in the Musée de l’Homme.


Descartes lived during a very skeptical period, at a time before science as we know it existed, and after a long period of relative stagnation in philosophical thought during the Church-dominated and Aristotle-influenced late Middle Ages. He had been impressed, in both his academic work and in his experience of the world at large, by the realization that there appeared to be no certain way of acquiring knowledge, and he saw his main task as the epistemological one of establishing what might be certain knowledge as a stepping stone towards the ultimate pursuit of truth. His more immediate aim in this was to put scientific enquiry in a position where it was no longer subject to attack by Skeptics, and he tried to do this by a kind of pre-emptive Skepticism, essentially by being more skeptical than the Skeptics.

At the heart of Descartes’ philosophical method was his refusal to accept the authority of previous philosophers, and even of the evidence of his own senses, and to trust only that which was clearly and distinctly seen to be beyond any doubt(a process often referred to as methodological skepticism or Cartesian doubt or hyperbolic doubt). Only then did he allow himself to reconstruct knowledge (piece by piece, such that at no stage was the possibility of doubt allowed to creep back in) in order to acquire a firm foundation for genuine knowledge and to dispel any Skepticism.

He outlined four main rules for himself in his thinking:

  • Never accept anything except clear and distinct ideas.
  • Divide each problem into as many parts are needed to solve it.
  • Order your thoughts from the simple to the complex.
  • Always check thoroughly for oversights.

Using this process, which he detailed in his epochal “Discourse on the Method” of 1637 and expanded in the “Meditations on First Philosophy” of 1641, Descartes attempted to narrow down, by what is sometimes called the method of doubt, what was certain and what contained even a shadow of a doubt. For example, he realized that he could doubt even something as apparently fundamental as whether he had a body (it could be that he was just dreaming of it or that it was an illusion created by an evil demon), but he could not, under any circumstances, doubt whether he had a mind or that he could think. He followed this up with a pure, abstract thought experiment. He imagined an evil spirit (or “deceiving demon”) whose sole intention was to mislead him, and asked whether there was anything about which the demon would not be able to mislead him. His conclusion was the act of thinking, that the demon could never make him believe that he was thinking when he was not (because, after all, even a false thought is still a thought).

Having identified this single indubitable principle, that thought exists, he then argued that, if someone was wondering whether or not he existed, then the very act of thinking was, in and of itself, proof that he did in fact exist: the famous “Je pense, donc je suis” (“I think, therefore I am”) – the similar statement in Latin, “Cogito ergo sum” is found in his later “Principles of Philosophy”. It is worth mentioning here that, by “thinking”, Descartes did not just mean conceptual thought, but all forms of consciousness, experience, feelings, etc.

Having dispelled all doubt by this process, Descartes then worked to build up, or reconstitute, the world again. But he was careful not to do this willy-nilly, but only according to his own very strict rules, so that the “reconstituted world” was not the same as the original one which he had dismantled piece by piece due to doubts. The way he achieved this (which, it must be said, appears from a modern viewpoint like something of a conjuring trick) was to argue that among the contents of our (certain) consciousness was the idea of God, which in itself he saw as proof of the existence of God. He then argued that, if we have the overwhelming impression of the existence of a concrete world around us, as we do, then an omnipotent, omniscient and omnibenevolent God would ensure that such a world does in fact exist for us. Furthermore, he asserted that the essence of this physical world was extension (that it takes up space), contrary to the extensionless world of the mind.

Paradoxically, this was an essential step forward in 17th Century science as it established a physical world which was of a mathematical character and permitted mathematical physics to be used to explain it. Also important is that, as we have seen, although God was indispensible to Descartes’ method of arriving at a physical world, once such a world was accepted, it was no longer necessary to involve God in the description and measurement and explanation of how things work. Thus, the process of science was freed from theological contraints and interference.

Descartes dismissed the senses and perception as unreliable, and to demonstrate this he used the so-called Wax Argument. This revolves around the idea that a wax object, which has certain properties of size, colour, smell, temperature, etc, appears to change almost all of these properties when it is melted, to the extent that it appears to our senses to be a completely different thing. However, we know that it is in fact still the same piece of wax. Descartes concluded from this that the senses can be misleading and that reason and deduction is the only reliable method of attaining knowledge, which is the essence of Rationalism.

Descartes further argued that sensory perceptions come to him involuntarily (not willed by him), and are therefore external to his senses and therefore evidence of the existence of an external world outside of his mind. He argued that the things in the external world are material because God would not deceive him as to the ideas that are being transmitted, and has given him the propensity to believe that such ideas are caused by material things. Because of this belief that God is benevolent and does not desire to deceive him, he can therefore have some faith in the account of reality his senses provide him.

Descartes believed that the human body works like a machine, that it has the material properties of extension and motion, and that it follows the laws of physics. The pieces of the human machine, he argued, are like clockwork mechanisms, and that the machine could be understood by taking its pieces apart, studying them, and then putting them back together to see the larger picture (an idea referred to as Reductionism). The mind or soul, on the other hand, is a non-material entity that lacks extension and motion, and does not follow the laws of physics.

Descartes was the first to formulate the mind-body problem in the form in which it exists today (see the section on Philosophy of Mind), and the first to clearly identify the mind with consciousness and self-awareness, and to distinguish this from the brain, which was the physical seat of intelligence (Dualism). In his epistemological work in the “Discourse on the Method”, he had realized that, although he could doubt that he possessed a body, he could not under any circumstances doubt that he possessed a mind, which led him to conclude that the mind and the body were two very different and separate things. His particular form of Dualism (known as Cartesian Dualism) proposed that the mind controls the body, but that the body also influences the otherwise rational mind (such as when people act out of passion) in a kind of two-way interaction, which he claimed, without much evidence, occurred in the pineal gland. Gilbert Ryle later described this kind of Dualism (where mental activity carries on in parallel to physical action, but where their means of interaction are unknown or, at best, speculative) as the “ghost in the machine”. Although his own solution was far from convincing, this kind of Cartesian Dualism set the agenda for philosophical discussion of the mind-body problem for many years after Descartes’ death.

It should be noted, however, that for all Descartes’ innovation and boldness, he does not abandon the traditional idea of God. He defined “substance” (essentially meaning what the world really consists of) as “that which requires nothing other than itself in order to exist”, but he concluded that the only true substance was God himself, because everything else (from souls to material objects like the human body) was dependent on God for its existence. He used his own variations of the causal argument, the ontological argument and the cosmological argumentfor the existence of God in his “Meditations” (see the section on Philosophy of Religion), and the existence of God played a major role in his validation of reason and in other parts of Descartes’ system. Given the important rôle God plays in his work, suggestions that Descartes was really a closet atheist, and that he includes the arguments for the existence of God as window dressing, appear extremely unlikley.

In mathematics, Descartes realized that a graph could be drawn to show a geometrical interpretation of a mathematical function using points known as Cartesian coordinates, and thereby founded analytic geometry or Cartesian geometry (using algebra to describe geometry), which was crucial to the subsequent development of calculus by Sir Isaac Newton (1643 – 1727) and Gottfried Leibniz. He also invented the notation which uses superscripts to indicate powers or exponents, and his rule of signs is also a commonly used method to determine the number of positive and negative zeros of a polynomial. It can be argued that his reflections on mind and mechanism, impelled by the invention of the electronic computer and by the possibility of machine intelligence, blossomed into the Turing test of a machine’s capability to demonstrate intelligence.

In optics, he showed by using geometric construction and the law of refraction(also known as Descartes’ law) that the angular radius of a rainbow is 42 degrees. He also independently discovered the law of reflection (that the angle of incidence equals the angle of reflection).

In physics, Descartes introduced (before Newton) the concept of momentum of a moving body (what he termed the “amount of motion”), which he defined as the product of the mass of the body and its velocity or speed. His three “laws of nature” became the basis of Newton’s later laws of motion and the modern theory of dynamics: that each thing tries to remain in the same state and, once moved, continues to move; that all movement is along straight lines; and that when a body comes into contact with another body the combined “quantity of motion” remain the same (his conservation of motion principle).

In an attempt to explain the orbits of planets, Descartes also constructed his vortex theory which would become the most popular theory of planetary motion of the late 17th Century (although subsequently discredited). However, he continued to cling to the traditional mechanical philosophy of the 17th Century, which held that everything physical in the universe to be made of tiny “corpuscles” of matter (although, unlike Atomism, the theory maintained that there could be no vacuum, just a mass of swirling matter).

Thomas Hobbes (1588 – 1679)


Thomas_HobbesThomas Hobbes (1588 – 1679) was an English philosopher of the Age of Reason. His famous 1651 book “Leviathan” and his social contract theory, developed during the tumultuous times around the English Civil War, established the foundation for most of Western Political Philosophy.

His vision of the world was strikingly original at the time, and is still relevant to contemporary politics. He did not shrink from addressing sensitive issues head on, and while few have liked his thesis, many have seen the political realism it represents.

Like Machiavelli before him, Hobbes looked on politics as a secular discipline, divorced from theology, and he has always attracted his share of powerful (and often vitriolic) detractors. Other have taken issue with his apparent assumption of mankind as not inherently benevolent, but rather self-centred and competitive.


Thomas Hobbes was born prematurely in Malmesbury, Wiltshire, England on 5 April 1588. His father, also Thomas, was the vicar of Charlton and Westport, but he abandoned his three children to the care of his older brother, Francis Hobbes, and fleed to London after an altercation outside his own church. Nothing is known of his mother.

Luckily, Francis was wealthy enough to provide for Thomas’ education, and he was educated at Westport Church from the age of four, before passing to Malmesbury School and then to a private school kept by a young man named Robert Latimer, a graduate of Oxford University. Hobbes was a good pupil and, around 1603, he moved to Magdalen College, Oxford to continue his education. He was little attracted by the Scholastic learning of the day, and largely pursued his own curriculum, graduating in 1608. Sir James Hussey, his master at Magdalen, recommended him as tutor to William, the son of William Cavendish, Baron of Hardwick (and later Earl of Devonshire), and began a life-long connection with that family.

In 1610, as companion to the younger William, he undertook a grand tour of Europe, where he was exposed to European scientific and critical methods (in contrast to the Scholastic philosophy which he had learned in Oxford). Although he associated with literary and philosophical figures such as Ben Jonson (1572 – 1637) and Sir Francis Bacon (and shared Bacon’s Atomist beliefs for a time), he did not extend his efforts into philosophy until after 1629. His only output before that time was the first English translation of the “History of the Peloponnesian War” by the ancient Greek historian Thucydides, which was published in 1628.

After his employer, the Earl of Devonshire, died of the plague in June 1628, the widowed countess dismissed Hobbes, but he soon found work as tutor to the son of Sir Gervase Clifton. This time, chiefly spent in Paris, ended in 1631, when he again found work with the Cavendish family, tutoring the son of his previous pupil. Over the next seven years, as well as tutoring, he expanded his own knowledge of philosophy, including a visit to Florence in 1636 and attendance at regular philosophical debates in Paris.

During these years, he first developed a theory of physical motion and momentum(although disdaining any experimental work in physics), and then extended this to the more human phenomena of sensation, knowledge, affections and passions, and from there he began to consider the sociological and political aspects of human interaction. The first two parts of his three-part treatise, “Human Nature” and “De Corpore Publico”, were written in 1640, but, before publishing them, and in the light of the uncertain political climate in the run up to the English Civil War of 1642 – 1651, he cautiously decided to move to Paris, where he remained for the next 11 years. There, he continued to work on his treatise, critiqued and corresponded with René Descartes among others, and developed a good reputation in philosophic circles.

When the Royalist cause in the English Civil War began to decline in the middle of 1644, there was an exodus of the king’s supporters to Europe, and especially to Paris. Hobbes’s political interests were revitalised, and the third (and most political) part of his three-part treatise, “De Cive”, was republished and more widely distributed in 1646. In 1647, after some months as mathematical instructor to the young Charles, Prince of Wales (later to become Charles II of England), he was persuaded by his Royalist friends to set forth his theory of civil government in detail, especially in relation to the political crisis resulting from the Civil War. Despite a serious illness which disabled him for six months, he continued in this task until 1651, when his famous masterwork “Leviathan” was published.

The work had immediate impact, and soon Hobbes was both more lauded and decried than any other thinker of his time. The secularist spirit of his book greatly angered both Anglicans and French Catholics, and he was ulimately forced to fleethe exiled royalists back to England and to appeal to the new revolutionary English government for protection.

From the age of about sixty, he began to suffer “shaking palsy” (probably Parkinson’s Disease), which steadily worsened over the years. In addition to publishing some ill-founded and controversial writings on mathematics and physics, Hobbes also continued to produce and publish philosophical works. “Behemoth”, published posthumously in 1682, though written rather earlier, was his account of England’s Civil Wars.

From the time of the Restoration of the monarchy in 1660, he acquired a new prominence, and his former pupil, now Charles II, remembered Hobbes and called him to the court to grant him a pension of £100. The king was also important in protecting Hobbes when, in 1666, the House of Commons introduced a bill against Atheism and profaneness, which specifically targeted “Leviathan”. In the end, the only consequence was that Hobbes was disallowed from publishing anything in England on subjects relating to human conduct (including even responses to the attacks of his enemies), and later editions of his works were printed in Amsterdam. Despite this, his reputation abroad remained formidable.

His final works were a curious mixture: an autobiography in Latin verse in 1672, and a translation of the “Iliad” and the “Odyssey” in 1675. In October 1679, Hobbes suffered a bladder disorder, which was followed by a paralytic stroke from which he died on 4 December 1679 in Derbyshire, England, aged 91.


Hobbes was not (as many have charged) an atheist, but he had a boundless contempt for Scholastic philosophy and the speculations of the Scholastics, (with their combinations of Christian theology and Aristotelian Metaphysics), and he was insistent that theological disputes should be kept out of politics. He also adopted a strongly Materialist metaphysics, which made it difficult to account for God’s existence as a spiritual entity. He claimed there is no natural source of authority to order our lives, and that human judgment is inherently unreliable, and therefore needs to be guided.

He was deeply influenced by the new deterministic science of the age (Galileo, Newton, Boyle, Hooke, etc) and by the certainty of mathematics. He was interested in constructing a completely mechanical model of the universe and, after visiting Galileo Galilei (1564 – 1642), he came to believe that the entire physical world could be explained by the new science of motion. He further believed that the human body was also explicable as a dynamic system, as were even the workings of the mind and the whole of civil society.

In his “Leviathan” (subtitled “The Matter, Form and Power of a Commonwealth, Ecclesiastical and Civil”) of 1651, Hobbes set out his doctrine of the foundation of states and legitimate governments, based on social contract theories (Contractarianism). It was written during the English Civil War of 1642 – 1651, and much of the book is occupied with demonstrating the necessity of a strong central authority and the avoidance of the evils of discord and civil war. It built on the earlier “Elements of Law” of 1640, (which was initially an attempt to provide arguments supporting the King against his challengers), and particularly on his “De Cive” of 1642.

He argued that the human body is like a machine, and that political organization (“commonwealth”) is like an artificial human being. Beginning from this mechanistic understanding of human beings and the passions, Hobbes postulated what life would be like without government, a condition which he called the “state of nature” and which he argued inevitably leads to conflict and lives that are “solitary, poor, nasty, brutish, and short”. In order to escape this state of war and insecurity, men in the state of nature accede to a “social contract” and establish a civil society. Thus, all individuals in that society cede their natural rights for the sake of protection, and any abuses of power by this authority must be accepted as the price of peace (although in severe cases of abuse, rebellion is to be expected). In particular, he rejected the doctrine of separation of powers, arguing that the sovereign must control civil, military, judicial and ecclesiastical powers, which some have seen as a justification for authoritarianism and even Totalitarianism.

Thus, Hobbes’ ethical views were based on the premise that what we ought to do depends greatly on the situation in which we find ourselves: where political authority is lacking (as in his famous natural condition of mankind), our fundamental right is self-preservation (to save our skins by whatever means we think fit); where political authority exists, however, our duty is merely to obey those in power.

In other fields, he was also known as a scientist (especially in optics), as a mathematician (especially in geometry, although some of his mathematical work has been unceremoniously slammed as inadequate and unrigorous), as a translator of the classics, and as a writer on law.