Plato (c. 427-347 BC) was born into a wealthy and aristocratic Athenian family. He cherished the ambition of entering politics when he came of age, but was disillusioned first by the injustices of the oligarchic government in which his relatives Charmides and Critias were involved, and later by the action of the democracy which succeeded it, particularly the trial and execution of Socrates in 399 BC. In his best-known dialogue, The Republic, he sought to provide a theoretical foundation for a government which would embody the justice he had found to be lacking in the actual governments of his day. His only active intervention in politics, in the intended role of adviser, was an unsuccessful one in Syracuse, Sicily. Details of it are given in his Seventh Letter. Some time before his second visit to Sicily, in 367 BC, he founded the school known as ‘the Academy’. His career as a writer of dialogues may have begun before this. In his early dialogues, he memorialized Socrates and his method of philosophizing by making him chief participant and questioner. His teaching in the Academy was interrupted for a third visit to Sicily in 361-360 BC, when he was nearly seventy. He survived an illness caused by the hardships of the journey, and died aged about eighty-one.

The long section on knowledge and the philosopher in books V–VII of the Republic is undoubtedly the most famous passage in Plato's work. So it is perhaps a good idea to begin by stressing how very peculiar, and in many ways elusive, it is. It is exciting, and stimulating, but extremely hard to understand.

Why should I be just? What have I to gain if I am decent, honest, moral, upright, fair and truthful? Other people benefit if I am just, but do I? And doesn't it seem clear that sometimes the benefit that other people receive from my being just is a benefit received at my expense? Perhaps then I have no adequate reason to be just. Perhaps if I have any sense I will not bother.

Aristotle (384–322 BC) was born in Stagira, Macedonia. He went to Athens and entered Plato's Academy when he was eighteen. He remained there until Plato's death in about 347 BC, when he left Athens to spend the next five years at Assos in Asia Minor and at Mytilene on the island of Lesbos, working on philosophy and biology. In 343 he was invited to return to Macedonia to tutor the son of Philip II of Macedonia, the future Alexander the Great. This lasted three or four years. After a further period at Stagira, Aristotle returned to Athens where he opened a philosophical school at the Lyceum or Peripatos. On the death of Alexander in 323 there was anti-Macedonian feeling in Athens, and to avoid the same fate as Socrates, Aristotle took refuge in Chalcis on the island of Euboea, leaving the school in the charge of his pupil Theophrastus. He died the following year.

Our understanding of the moral philosophy of Aristotle is hampered by a number of modern assumptions we make about the subject. For a start, we are accustomed to thinking about ethics or moral philosophy as being concerned with theoretical questions about actions—what makes an action right or wrong? Modern moral philosophy gives two different sorts of answers to this question. One is in terms of a substantial ethical theory—what makes an action right or wrong is whether it promotes the greatest happiness, or whether it is in accordance with or violates a moral rule, or whether it promotes or violates a moral right. The other sort gives a meta-ethical answer—rightness and wrongness are not really properties of actions, but in describing actions as right or wrong we commend or object to them, express our approval or disapproval or our emotions concerning them. But the ancient Greeks start with a totally different question. Ethics is supposed to answer, for each one of us, the question ‘How am I to live well?’ What this question means calls for some discussion.

René Descartes (1596–1650) was born at La Haye, near Tours in France. He entered the Jesuit School at La Flèche in 1606, where he studied Latin and Greek and the classical authors, and acquired respect for the certainty of mathematics and distaste for the theories of Aristotle as developed by medieval commentators. In 1616, he took a degree in law at the University of Poitiers. There followed a period during which he travelled, for some of the time as a gentleman-officer in the armies of Maurice of Nassau, Prince of Orange, and Maximilian, Duke of Bavaria. In 1625 he returned to Paris and renewed his acquaintance with Father Marin Mersenne, who was later instrumental in making his views known to many of the famous intellectuals in Europe. From 1628 to 1649 he lived in Holland and worked out in detail the scientific, philosophical and mathematical ideas that had engaged him during his travels. His main philosophical works are Rules for the Direction of the Mind, written in 1629–30 but not published until 1684, Discourse on Method, 1637, Meditations, 1641, Principles of Philosophy, 1644, and The Passions of the Soul, 1649. In 1649, Descartes accepted an invitation to visit the Queen of Sweden and instruct her in philosophy. He succumbed to the rigorous climate, and died in February 1650.

Descartes published his Meditations in First Philosophy in 1641. A French translation from the original Latin, which he saw and approved, followed six years later. The words ‘in First Philosophy’ indicate that the Meditations attack fundamental questions, the chief of them being the nature of knowledge and the nature of man. I shall deal almost entirely with his treatment of the first, the nature of knowledge; even when the two questions become mixed up, as they notoriously do, I shall not encroach on to the second, the nature of man. The Meditations were intended to confirm Descartes' reputation as a philosopher (he was already pre-eminent as a mathematician and a scientist) and, to increase their impact, they were accompanied in their first publication by a series of comments solicited from notable theologians and philosophers together with Descartes' replies. These comments are called the Objections and numbered from one to six, but it is only an accident that there are six Meditations and six Objections. There are six Objections because there are six objectors (that is not quite true, the sixth Objection being a collection of comments from several people) and each Objection ranges over the whole work, although, of course, the different commentators focused upon the parts they found important or questionable. Many of the Objections, particularly those of Arnauld and Gassendi, contain acute and valuable criticisms. Descartes took exception to Gassendi's contribution and wished not to have it published. He maintained that Gassendi quite misunderstood him, but that doesn't seem true. It is true that Gassendi pokes fun at Descartes in addressing him first ‘O Soul’ and later, pretending to realize his mistake, ‘O Mind’, but no doubt the trouble was that Gassendi understood rather too well, fastening upon inconsequentialities in the argument and inconsistencies in the thought and finding, against both, formidable arguments. Inconsequentialities and inconsistencies there are, so much so that the work is a set of parts rested together to give the appearance of a construction, not fitted together really to make one. That did not prevent the Meditations having as great an influence on philosophical thought as any work from the day of its publication to our own, or prevent Descartes' ideas from occupying the minds of philosophers ever since.

The Sixth Meditation deals, as its title proclaims, with ‘the existence of material things, and the real distinction between the mind and body of man’. In this paper, I want to start by examining Descartes' argument for the existence of material things—for the existence of an ‘external’, physical world around us. Next, in section two, I shall use this argument concerning the external world to bring out an important general point about the ‘dialectical’ way in which Descartes presents his reasoning in the Meditations. This will lead me on to the third section of the paper, which will analyse the concept of ‘nature’ and the role it plays in Descartes' reasoning, particularly in the Sixth Meditation. And this in turn will bring me to the fourth and final part of the paper, which will focus on what is by general consensus the most fascinating part of the Sixth Meditation—Descartes' account of the relation between mind and body. What I shall try to do in this final section is to highlight a curious tension between Descartes' recognition of the facts of human experience on the one hand, and on the other hand his doctrine that we are essentially incorporeal or non-physical substances.

David Hume (1711–1776) was born in Scotland and attended Edinburgh University. In 1734, after a brief spell in a merchant's office in Bristol, he went to France to write A Treatise of Human Nature, published anonymously in 1739 (Books I and II) and 1740 (Book III). An Abstract, also anonymous and written as if by someone other than the author of the Treatise, appeared about the same time, and provides an invaluable account, in a brief compass, of what Hume thought most important about the Treatise. The Treatise was not well received, and Hume was unsuccessful in his candidature for the chair of moral philosophy at Edinburgh. He rewrote Book I of the Treatise, adding a controversial discussion of miracles and providence; and a revision of this was published as An Enquiry Concerning Human Understanding in 1748. His Enquiry Concerning the Principles of Morals, which was a rewriting of Book III of the Treatise, was published in 1751, and his Dissertation on the Passions, corresponding to Book II of the Treatise, but with significant omissions, such as the account of the psychological mechanism of sympathy, in 1757. In 1752 he had been made keeper of the Advocates' Library at Edinburgh, and wrote his History of England which, at the time, brought him more approbation than his philosophy. During this time, he wrote the Dialogues Concerning Natural Religion, published posthumously in 1779. In 1763 he became secretary to the British Embassy in Paris. He returned to London in 1766, and a year later was Undersecretary of State. In 1769 he returned to Edinburgh and worked on final editions of his writings, and on an autobiography, dated 18 April 1776, a few months before his death.

I. Two topics given prominence in the early sections of Hume's Enquiry Concerning Human Understanding are those of thought and belief. Of each Hume asks two questions. One, which we might call the constitutive question: what exactly is it to have a thought, or to hold a belief?—and another, which we may call the genetic question: how do we come by our thoughts, or our capacity to think them, and how do we come to believe that certain of these thoughts are true? In this lecture I shall be considering the detail of Hume's answers to these questions; but first I want to say a little about why they should have loomed large for him at all.

David Hume (1711–1776) described the question of liberty and necessity as ‘the most contentious question of metaphysics, the most contentious science’ (Hume [1748] 1975, p. 95). He was right about it being contentious. Whether it is metaphysical is another matter. I think that what is genuinely metaphysical is an assumption that Hume, and a good many other philosophers, make in their treatment of the question. The assumption is about language and reality. I call it ‘the conformity assumption’. But more about that shortly. Let us begin at the obvious beginning, by considering what the terms ‘liberty’ and ‘necessity’ mean in the expression ‘liberty and necessity’.

I shall be dealing with not only Sections X and XI but also Part II of Section VIII and Part III of Section XII. Of all this material we have, anywhere in the originally anonymous and later emphatically disowned Treatise of Human Nature, Hume's first book, nothing more than at most hints. But in a surviving letter, written while he was still working on the manuscript of that Treatise, Hume wrote: ‘I am at present castrating my work, that is, cutting off its nobler parts; that is, endeavouring it shall give as little offence as possible, before which I would not pretend to put it in the Doctor's hands’. Enclosed with this letter were some ‘Reasonings concerning Miracles’, which must have anticipated what became Section X of our Enquiry. Presumably there were other excised anticipations also. The ‘Doctor’ mentioned was a Doctor of Theology, Joseph Butler, soon to be appointed Bishop of Durham; an office open in that period only to believing Christians.

Karl Marx (1818–1883) was born in Trèves in the Rhineland. He studied law in Bonn, philosophy and history in Berlin, and received a doctorate from the University of Jena for a thesis on Epicurus (341–270 BC). (Epicurus' philosophy was a reaction against the ‘other-worldliness’ of Plato's theory of Forms. Whereas for Plato knowledge was of intelligible Forms, and the criterion of the truth of a hypothesis about the definition of a Form was that it should survive a Socratic testing by question and answer, for Epicurus the criterion of truth was sensation, and employment of this criterion favoured the theory with which Plato explicitly contrasted the theory of Forms (Sophist 246a–d), namely, the materialism of the atomists, Leucippus and Democritus.) Marx was editor of the Rheinische Zeitung of Cologne, 1842–1843. The paper was suppressed and he moved to Paris, becoming co-editor of the Deutsch-französische Jahrbücher, the one and only issue of which contained two articles by Marx and two by his friend, Friedrich Engels (1829–1895). Together they wrote The German Ideology (1846) and their most influential work, The Communist Manifesto (1848). Marx had been expelled from France in 1845, and went to Brussels, from where he was expelled during the 1848 revolutions. He went to Cologne to start, with Engels and others, a paper with a revolutionary editorial policy, the Neue Rheinische Zeitung. Expelled once again, Marx finally settled in London, working in the British Museum on his great historical analysis of capitalism, Das Kapital. The first volume was published in 1867, the remaining two volumes, completed by Engels after Marx's death, in 1885 and 1895.

The texts before us are relatively early works. They predate the famous Manifesto of the Communist Party of 1848. Their importance lies in this: that here historical materialism is outlined and defended for the first time. This new philosophy is elaborated in the course of Marx and Engels' effort to settle accounts with previous German philosophy—and, perhaps, with philosophy as such. The new outlook is developed, therefore, in the context of polemic against Hegel and Feuerbach, precisely the thinkers that they most admired earlier in fact.

John Stuart Mill (1806–1873) was born in London, son of the Scottish historian of India and philosopher, James Mill, by whom he was educated in, among other things, the principles of British empiricism and Benthamite utilitarianism. Like his father, he worked for the East India Company, being in charge of the Company's relations with the native states 1836–1856, and head of the examiner's office from 1856 until the powers of the Company were transferred in 1858. The book which established Mill as a philosopher was his System of Logic (1843), described in its full title as ‘a connected view of the principles of evidence and the methods of scientific investigation’. Book 6 of the System of Logic was ‘On the logic of the moral sciences’, and at the end of it Mill declared, without trying to justify it, his opinion that there is a ‘general principle to which all rules of practice ought to conform’; namely that of ‘conduciveness to the happiness of mankind, or rather, of all sentient beings’. For example, we should keep our promises not because we can see intuitively the truth of the precept, but because it passes the utilitarian test. Mill's justification for this opinion was in his Utilitarianism (1863). Mill's version of utilitarianism differed from Bentham's in that he recognized not only quantitative but also qualitative differences between pleasures.

John Stuart Mill is—surprisingly—a difficult writer. He writes clearly, non-technically, and in a very plain prose which Bertrand Russell once described as a model for philosophers. It is never hard to see what the general drift of the argument is, and never hard to see which side he is on. He is, none the less, a difficult writer because his clarity hides complicated arguments and assumptions which often take a good deal of unpicking. And when we have done that unpicking, the task of analysing the merits and deficiencies of the arguments is still only half completed. This is true of all his work and particularly true of Liberty. It is an essay whose clarity and energy have made it the most popular of all Mill's work. Yet it conceals philosophical, sociological and historical assumptions of a very debatable kind. In his introduction, Mill says

the object of this essay is to defend one very simple principle, as entitled to govern absolutely the dealings of society with the individual in the way of compulsion and control, whether the means used be legal penalties, or the moral coercion of public opinion (Liberty, 68).

Friedrich Nietzsche (1844–1900) was born in the village of Röcken, in Prussian Saxony, the son and grandson of Lutheran ministers. He studied theology and classical philosophy at the University of Bonn, but in 1865 he gave up theology and went to Leipzig. Then he discovered the composer Richard Wagner and the philosophers Schopenhauer and F. A. Lange (author of History of Materialism and Critique of its Present Significance, 1866). He won a prize for an essay on Diogenes Laertius, the biographer of ancient Greek philosophers, and was appointed associate professor of classical philology at Basel, when he was only twenty-four. He became a full professor the following year. His principle writings between then and 1879, when illness made him resign from the university, were The Birth of Tragedy (1872) and Human, All Too Human (1878). After his resignation his principal writings were Daybreak (1881), The Gay Science (1882), Thus Spoke Zarathustra (Parts 1 and 2 published 1883, Part 3 published 1884, Part 4 issued privately 1885, published 1892), Beyond Good and Evil (1886), On the Genealogy of Morals (1887), The Wagner Case (1888) and Twilight of the Idols (1888). Nietzsche became insane in January 1889, and vegetated until his death in 1900. His madness was probably tertiary syphilis, which he may have contracted while ministering to sick soldiers in 1870 as a medical orderly in the Franco-Prussian war.

Although Nietzsche's greatness is recognized more universally now than ever before, the nature of that greatness is still widely misunderstood, and that unfortunately means that before I discuss any of Beyond Good and Evil (henceforth BGE) in any detail, I must make some general remarks about his work, his development and the kind of way in which I think that it is best to read him. Unlike any of the other philosophers that this series includes, except Marx and Engels, Nietzsche is very much concerned to address his contemporaries, because he was aware of a specific historical predicament, one which he would only see as having worsened in ways which he predicted with astonishing precision in the century since he wrote his great series of works. For he was above all a philosopher of culture, which is to say that his primary concern was always with the forces that determine the nature of a particular civilization, and with the possibilities of achievement which that civilization consequently had open to it. One of the reasons that The Birth of Tragedy, his first book, published when he was twenty-eight, created such a surge of hostility in the world of classical scholarship was that in it, whilst undertaking an investigation of what made possible the achievements of fifth century BC Greece in tragic drama, he felt it necessary to elicit the whole set of fundamental beliefs which the Greeks shared, and also to draw metaphysical conclusions from the fact that they were able to experience life in such a way that they needed great tragedies in order to endure it.

Bertrand Russell (1872–1970), born in Trelleck, Wales, was the grandson of the first Earl Russell, who introduced the Reform Bill of 1832 and served as prime minister under Queen Victoria. He studied mathematics and philosophy at Trinity College, Cambridge, 1890–1894, was a Fellow of Trinity College, 1895–1901, a Fellow of the Royal Society in 1908, and was a lecturer in philosophy, 1910–1916. Among his publications in philosophy in this period were An Essay on the Foundations of Geometry (1897), A Critical Exposition of the Philosophy of Leibniz (1900), The Principles of Mathematics (1903), Principia Mathematica (with A. N. Whitehead, 1910–1913), The Problems of Philosophy (1912) and Our Knowledge of the External World (1914).