Early Modern Philosophy

Early modern philosophy is the philosophy of Europe from about 1600 to the middle of the eighteenth century. It grew up alongside the Scientific Revolution, and its leading figures were often scientists and mathematicians as well as philosophers. Its centres were the Dutch Republic, where printers published what others dared not, Paris, London and later Edinburgh, with thinkers moving constantly between them by letter and in person. The century in which it flourished was also one of war: the Thirty Years' War devastated Germany, and England passed through civil war, the rule of Oliver Cromwell, restoration and the Glorious Revolution.

These thinkers set out to replace the Aristotelian philosophy still taught in the universities with something built on firmer foundations. They asked what human beings can know and how, what the world must be like if the new mathematical physics is true, how mind relates to body, whether God's existence can be proved, and what gives a state the right to rule. Later historians sorted them into two camps, continental rationalists who trusted reason and British empiricists who trusted experience. That division is too neat, but it captures a real argument, and the questions they raised still shape philosophy. The era follows Renaissance Philosophy and overlaps with The Enlightenment, which took up its ideas and applied them to society.

By 1600 the intellectual order of the Middle Ages was in pieces. The Protestant Reformation had split the Western church, and each side accused the other of error, raising the question of how religious truth could be known at all. The sceptical arguments of ancient Pyrrhonism, revived by Michel de Montaigne and his followers, suggested that neither the senses nor reason could be trusted. And astronomy was undermining Aristotle's picture of the cosmos. Nicolaus Copernicus had put the Sun at the centre of the planetary system, Johannes Kepler had shown that the planets move in ellipses, and Galileo Galilei had found moons around Jupiter and argued that nature is written in the language of mathematics. In 1633 the Roman Inquisition condemned Galileo and confined him to his villa near Florence for the rest of his life, a warning that reached every natural philosopher in Catholic Europe.

The response of the new philosophers was to look for a method: a way of reasoning that could resist sceptical doubt, settle disputes and produce reliable knowledge of nature.

Francis Bacon (1561 to 1626) was a lawyer and statesman who became Lord Chancellor of England under James I before his fall from office in 1621 on charges of taking bribes. In The Advancement of Learning (1605) and the New Organon (1620), whose title challenged Aristotle's logical works, known as the Organon, he argued that knowledge had stood still for two thousand years because philosophers built systems from a few hasty observations and then argued about words.

Bacon described four kinds of idols, habits of mind that distort understanding: those common to all humans, such as seeing more order than exists; those of the individual, from upbringing and temperament; those of the marketplace, from the loose use of language; and those of the theatre, from received philosophical systems. Against them he proposed a patient method of induction, collecting and comparing many instances, including negative ones, and rising only gradually to general laws. He saw science as a collective enterprise aimed at improving human life, and in his unfinished utopia New Atlantis imagined a state-funded research college. Bacon undervalued mathematics, but his vision inspired the founders of the Royal Society of London, chartered in 1662.

René Descartes (1596 to 1650) was educated by Jesuits at La Flèche in the Kingdom of France, served briefly as a soldier and spent most of his working life in the Dutch Republic. A mathematician of the first rank, he joined algebra and geometry by describing curves with equations. He had prepared a treatise on physics, The World, but withheld it on hearing of Galileo's condemnation. Instead he published the Discourse on the Method (1637) and, in Latin, the Meditations on First Philosophy (1641), circulated in advance by his friend the friar Marin Mersenne and printed with objections from leading scholars and Descartes's replies.

The Meditations begins by doubting everything that can be doubted: the senses, the existence of the body, even mathematics, since an all-powerful deceiving demon might be tricking him. One thing survives. While he doubts, he must exist, since he is thinking; in the Discourse this is put as I think, therefore I am. From this starting point Descartes argued that God exists, since the idea of a perfect being could not have come from an imperfect mind, and that a good God would not let us be deceived about what we perceive clearly and distinctly. Critics, including the theologian Antoine Arnauld, objected that this reasoning is circular: Descartes relies on clear perception to prove God, and on God to guarantee clear perception.

Descartes divided the world into two kinds of substance. Mind is a thinking thing, without size or shape. Matter is pure extension, length, breadth and depth, and everything in the physical world, including animal and human bodies, can be explained mechanically by the size, shape and motion of its parts, like a clock. This dualism cleared the way for a mathematical physics but left a problem: how can an unextended mind move an extended body? Descartes suggested that they interact in the pineal gland in the brain, an answer few found satisfying. In 1649 he accepted an invitation from Queen Christina of Sweden and died of pneumonia in Stockholm the following February.

The sharpest early objection to Descartes's dualism came from Princess Elisabeth of Bohemia (1618 to 1680). She was the daughter of Frederick V, the Elector Palatine whose acceptance of the Bohemian crown in 1619 helped start the Thirty Years' War, and she grew up in exile in The Hague. In 1643 she wrote to Descartes asking how a soul that has no extension can move a body, since motion seems to require contact, and contact requires a surface. Descartes's answers, that the union of mind and body is a primitive notion known through ordinary experience, did not satisfy her, and she suggested it would be easier to grant extension to the soul than to understand how something immaterial could move matter.

Their correspondence, which lasted until his death, went on to cover the passions, free will, the good life and Machiavelli. Descartes dedicated his Principles of Philosophy (1644) to her and wrote The Passions of the Soul partly in response to her questions. Elisabeth later became abbess of the Lutheran convent of Herford in Westphalia, where she gave refuge to religious dissenters. Only her side of the letters with Descartes, published in the nineteenth century, survives as her philosophical work, which helps explain why she was long overlooked.

Thomas Hobbes (1588 to 1679) worked for most of his life as tutor and secretary to the Cavendish family, the Earls of Devonshire. On a tour of Europe he discovered geometry, admired its method of proof, and in 1636 met Galileo in Florence. Hobbes was a thorough materialist. He held that everything that exists is body in motion, that thought itself is a motion in the head, and that words such as incorporeal substance are meaningless. He contributed a set of objections to Descartes's Meditations, and the two men disliked each other.

Fearing for his safety as the conflict between Charles I and Parliament grew, Hobbes left for Paris in 1640 and wrote his political masterpiece, Leviathan, published in 1651. He asked what life would be like without any government. In this state of nature, where people are roughly equal, competing for scarce goods and fearful of one another, there would be a war of every man against every man, and life would be solitary, poor, nasty, brutish and short. Reason therefore leads people to agree among themselves to hand their power to a sovereign, one person or an assembly, whose authority must be nearly unlimited, since a divided power leads back to civil war. Subjects may resist only to save their own lives. Leviathan scandalised royalists by grounding authority in consent rather than divine right, and churchmen by its materialism, but its method of deriving the state from human nature and agreement founded modern social contract theory.

Blaise Pascal (1623 to 1662) was a mathematical prodigy from Clermont who built one of the first calculating machines, founded with Pierre de Fermat the mathematics of probability, and demonstrated by experiment that a vacuum could exist, against the Aristotelian and Cartesian view that nature abhors one. After a mystical experience in November 1654 he devoted himself to religion and to the Jansenists of the convent of Port-Royal near Paris, a Catholic movement with a severe view of grace, defending them against the Jesuits in his witty Provincial Letters.

At his death he left notes for a defence of Christianity, published as the Pensées, or Thoughts. Pascal pictured humanity suspended between two infinities, the vastness of the universe and the endless divisibility of matter, and saw human beings as both wretched and great: a reed, the weakest thing in nature, but a thinking reed. Reason, he argued, cannot prove or disprove God, so the question is a wager. If God exists and you believe, you gain infinitely; if not, you lose little. The heart has its reasons, he wrote, that reason does not know. Pascal stands as a warning from inside the new science that it cannot answer every human question.

Baruch Spinoza (1632 to 1677) was born in Amsterdam to a family of Portuguese Jews who had fled the Inquisition. In 1656 the leaders of the synagogue issued a ban of exceptional severity against him, for reasons that are not fully recorded but probably included his denial that the soul is immortal and that the Law of Moses was given by God. He took the Latin name Benedictus, earned part of his living grinding lenses, and lived quietly in villages near Leiden and later in The Hague.

His Ethics, published after his death, is set out like Euclid's geometry, with definitions, axioms and proofs. Spinoza argued that there can be only one substance, infinite and self-caused, which he called God or Nature. Mind and body are not two substances but two ways of describing the same thing, under the attributes of thought and extension, which dissolves the problem that troubled Elisabeth. Everything follows necessarily from the nature of God, as the properties of a triangle follow from its definition; there is no free will in the ordinary sense and no purpose in nature. God is not a person who plans, judges or answers prayers. Freedom, for Spinoza, means understanding the causes that move us, and so being governed by reason rather than passion, and the highest happiness is an intellectual love of God.

His Theological-Political Treatise (1670), published anonymously, read the Bible as a historical document written by many human authors, argued that its purpose is to teach obedience and charity rather than truth about nature, and defended freedom of thought and democracy as the most natural form of government. It was banned across Europe. For a century the word Spinozist was an accusation of atheism, though some later readers, especially in Germany, saw him as intoxicated with God. In France Nicolas Malebranche took Cartesianism in another direction, holding that God is the only true cause and that mind and body do not act on each other at all.

Gottfried Wilhelm Leibniz (1646 to 1716), from Leipzig, served for forty years as librarian, historian and adviser to the dukes of Hanover, and helped found the scientific academy in Berlin. He invented the calculus in Paris in the mid-1670s, independently of Newton, and his notation is still used; a bitter dispute over who came first was decided in Newton's favour by a committee of the Royal Society that Newton himself guided. He also designed a calculating machine, worked on binary arithmetic and pursued plans to reunite the churches.

Leibniz published only one philosophical book in his lifetime, the Theodicy (1710), but his letters and essays, such as the short Monadology (1714), set out a striking system. The world is made not of extended matter but of countless simple, soul-like substances he called monads, each mirroring the whole universe from its own point of view. Monads do not interact; God has arranged them in advance so that their states correspond, like clocks set to the same time, a pre-established harmony. His principle of sufficient reason holds that nothing happens without a reason why it is so and not otherwise. Since God chose the best among all possible worlds, ours is the best possible, despite its evils, a claim Voltaire mocked in Candide. Against Newton's follower Samuel Clarke, in letters of 1715 and 1716, Leibniz argued that space is not an absolute container but merely the order of relations between things.

John Locke (1632 to 1704) trained as a physician at Oxford, worked with the chemist Robert Boyle, and served as secretary to the Earl of Shaftesbury, leader of the opposition to the Catholic heir James II. He fled to the Dutch Republic in 1683 and returned after the Glorious Revolution of 1688, when within months he published his major works.

His Essay Concerning Human Understanding rejected the rationalist belief in innate ideas. The mind at birth is like white paper, and all ideas come from experience, either sensation of the outside world or reflection on the mind's own workings. Complex ideas are built from simple ones. Locke distinguished primary qualities, such as shape, size and motion, which really belong to bodies, from secondary qualities, such as colour, taste and warmth, which are powers in bodies to produce sensations in us. He held that personal identity consists in continuity of consciousness and memory rather than of soul or body, and he was modest about what can be known with certainty, leaving much to probability.

In political thought Locke answered both Hobbes and the defenders of royal absolutism such as Robert Filmer. In the Two Treatises of Government he argued that people in the state of nature already have natural rights to life, liberty and property, given by God and knowable by reason. They form governments by consent to protect these rights, and a government that violates them may be resisted and replaced. His Letter Concerning Toleration (1689) argued that the state has no business forcing belief, though he excluded Catholics and atheists. These ideas fed directly into the American Revolution.

Beyond Elisabeth, several women took part in these debates, though barred from universities and often published anonymously or not at all. Margaret Cavendish, Duchess of Newcastle (1623 to 1673), spent the English Civil War in exile in Paris and Antwerp with her husband, whose brother's circle included Hobbes and Descartes. She published more than a dozen books under her own name, unusual for a woman of the time. She rejected both Cartesian dualism and the idea of inert matter, arguing that nature is wholly material but that all matter is self-moving and capable of perception and reason in its own way. In Observations upon Experimental Philosophy (1666) she criticised the microscope work of Robert Hooke, doubting that magnified images show nature as it really is, and she printed with it The Blazing World, an early work of science fiction. In 1667 she became the first woman to attend a meeting of the Royal Society.

Anne Conway (1631 to 1679), who studied with the Cambridge Platonist Henry More, developed a different system in a treatise published after her death. She held that there are three kinds of being, God, Christ as mediator, and creatures, and that the created world is a single continuum in which body and spirit differ only in degree, so that body is a kind of condensed spirit. She argued against Descartes, Hobbes and Spinoza, held that all creatures can grow in perfection, and influenced Leibniz, who praised her ideas. In England Mary Astell, writing in the 1690s, used Cartesian arguments about the equality of minds to argue for women's education.

Isaac Newton (1642 to 1727) published his Mathematical Principles of Natural Philosophy, usually called the Principia, in 1687. With three laws of motion and a law of universal gravitation, by which every body attracts every other with a force that weakens with the square of the distance, he explained the falling of objects on Earth, the orbits of planets, the tides and the paths of comets. It was the triumph of the mathematical physics that Galileo and Descartes had hoped for, but it differed from Descartes's in an important way. Newton could not explain how gravity acts across empty space, and refused to invent hypotheses about its cause; he described the force mathematically and justified it by its success in predicting observations.

Leibniz and the Cartesians objected that a force acting at a distance was a return to the occult qualities of scholastic philosophy. Newton's supporters replied that philosophy should follow the evidence rather than demand mechanical pictures. The Principia also asserted absolute space and time, against Leibniz's relational view. In the decades after his death Newton became the model for the Age of Enlightenment, a proof that patient inquiry could uncover the laws of nature.

The empiricist line was carried further by two thinkers from the British Isles. George Berkeley (1685 to 1753), an Anglican clergyman from Ireland who studied and taught at Trinity College in Dublin, argued in his Principles of Human Knowledge (1710) that Locke had not gone far enough. If all we ever perceive are ideas, and primary qualities are as dependent on perception as secondary ones, then the notion of matter existing unperceived is empty. For things like tables and trees, to be is to be perceived. The world does not vanish when no human is looking, because it is always perceived by God. Berkeley believed this immaterialism defended common sense and religion against sceptics and atheists. He later became Bishop of Cloyne.

David Hume (1711 to 1776), from Edinburgh in the Kingdom of Scotland, took empiricism to sceptical conclusions. His Treatise of Human Nature (1739 to 1740), written partly at La Flèche where Descartes had studied, sold so poorly that Hume said it fell dead-born from the press, and he recast it in shorter Enquiries. Hume argued that we never observe a necessary connection between cause and effect, only that one kind of event regularly follows another; our belief that the future will resemble the past rests on habit, not reason. Looking inward, he found no single self, only a bundle of perceptions. Reason alone cannot move us to act, he argued, and no conclusion about what ought to be follows from facts about what is. His reputation for religious scepticism cost him university posts at Edinburgh and Glasgow, and his Dialogues Concerning Natural Religion appeared only after his death.

Hume's arguments brought the era to a turning point. Immanuel Kant said that reading Hume woke him from his dogmatic slumber, and his critical philosophy of the 1780s tried to reconcile the rationalist and empiricist traditions by showing that experience itself is shaped by the structures of the mind. Hume's friend Adam Smith built on his moral psychology. Meanwhile the political theories of Hobbes, Spinoza and Locke, the Newtonian model of science and the critical reading of scripture passed into the wider movement of the Enlightenment.

The period left modern philosophy its basic agenda: the problem of knowledge, the relation of mind and body, the nature of causation and personal identity, the grounds of political authority and the place of God in a world described by physics. Recent scholarship has also restored figures such as Elisabeth, Cavendish and Conway to the story from which they were long left out. For the eras before and after, see The History of Philosophy.