Purely practical considerations ordain that we should not pursue our subject too far into its embryonic stage, or at least not to a time before its conception. What may we call the conception of Greek philosophy? It occurred when the conviction began to take shape in men's minds that the apparent chaos of events must conceal an underlying order, and that this order is the product of impersonal forces. To the mind of a pre-philosophical man, there is no special difficulty in accounting for the apparently haphazard nature of much that goes on in the world. He knows that he himself is a creature of impulse and emotion, actuated not only by reason but by desires, love, hatred, high spirits, jealousy, vindictiveness. What more natural than that the ways of the world around him should have a similar explanation? He sees himself to be at the mercy of superior and incomprehensible forces, which sometimes seem to act with little regard for consistency or justice. Doubtless they are the expression of beings like-minded with himself, only longer-lived and more powerful. Our present purpose does not require us to enter the troubled regions of anthropological controversy by suggesting that these remarks have any necessary bearing on the ultimate origin, or origins, of religious belief. All we have to notice is that these are the assumptions of that type of polytheism or polydaemonism which dominated the early mind of Greece and can be studied in all its picturesque detail in the Homeric poems. Everything there has a personal explanation, not only external and physical phenomena like rain and tempest, thunder and sunshine, illness and death, but also those overmastering psychological impulses through which a man feels no less that he is in the power of something beyond his own control. A guilty passion is the work of Aphrodite, an act of folly means that ‘Zeus took away his wits’, outstanding prowess on the field of battle is owed to the god who ‘breathed might into’ the hero.

To write a history of Greek philosophy is to describe the formative period of our own thought, the making of the framework which supported it until at least the latter part of the nineteenth century. The discoveries about the nature of matter (if that term may still be used), the size and character of the Universe, and the human psyche which scientists have been making during the last hundred years are indeed so revolutionary that they may result in a radical reshaping of our fundamental outlook. Apart, however, from the fact that they are still in such a state of rapid transition that it is difficult to see what this new framework of thought will be, the conservatism of ordinary human minds ensures that much in the older outlook will continue to colour our general presuppositions for a long time to come. Even the modem natural philosopher who studies the records of the earliest European thinkers may find that he has more in common with them than he expected. It is this fundamental and dateless character of much Greek thought which makes it worth while to attempt a fresh presentation of it for a contemporary reader.

There is another side to the coin. With the Greeks we stand at the beginning of rational thought in Europe. It follows that we shall not only be concerned with reasoned explanation or scientific observation, but shall be watching the emergence of these activities from the mists of a pre-scientific age. This emergence is not sudden, but slow and gradual. I shall try indeed to justify the traditional claim of Thales to be regarded as the first European philosopher; but I shall not intend by that to assert that at one bound the line was crossed between pre-rational, mythical or anthropomorphic conceptions and a purely rational and scientific outlook. No such clearly-marked line existed, or exists today. Besides appreciating what is of permanent value in Greek thought, we may also learn from observing how much latent mythology it continued to shelter within what appear to be a roof and walls of solid reason.

A student in any branch of knowledge who is invited to set before a popular audience, within the space of four hours, the gist and upshot of his studies, may do well to submit himself to the discipline implied. He knows that the expert will frown upon some of his statements as questionable in content and dogmatic in tone, and will mark the omission of many things for which no room could be found. But it will do him good to sit back in his chair and look for the main outline, so often obscured by detail. It seemed clear that Socrates must be taken as the central figure in the period allotted to me, and that my business was to convey the significance of his conversion of philosophy from the study of Nature to the study of human life. I have tried, accordingly, so to describe the early Ionian science as to show why it failed to satisfy Socrates, and I have treated the systems of Plato and Aristotle as attempts to carry into the interpretation of the world the consequences of Socrates' discovery. I have gained a fuller understanding of that discovery from M. Henri Bergson's book, Les deux sources de la morale et de la religion, which came into my hands when I was meditating these lectures.

Attracted to Athens by the fame of Plato, Aristotle came from his home in northern Greece in his eighteenth year to become a student of the Academy. Plato was then sixty and had been head of the school for at least fifteen years. No young student has ever been subject to the dominance of a more overpowering personality. Aristotle, of course, became a Platonist, and remained at the Academy for the next twenty years, as the pupil and then as the colleague of Plato, till Plato's death in 347 B.C. In imitation of his master, he wrote dialogues intended, like Plato's own earlier works, for the educated public throughout the Greek world. They were read and admired for centuries after his death; but they have not come down to us. We possess only enough fragments, preserved by other writers, to show us that Aristotle, in this first period of his career, was a whole-hearted Platonist, accepting the theory of ideal Forms, which he was afterwards to renounce.

When Plato died, the headship of the Academy passed to his nephew Speusippus, a man of no marked originality. We have no record of Aristotle's feelings upon the promotion of a colleague immeasurably inferior to himself. We only know that he left Athens with Xenocrates, who was later to succeed Speusippus, and that his attitude towards the Academy, and even towards Platonism, became increasingly antagonistic.

In this course of lectures it falls to me to speak of the whole creative period of Greek philosophy—of the Ionian science of Nature before Socrates, of Socrates himself, and of his chief followers, Plato and his pupil Aristotle. I cannot attempt even a bare outline of the history of thought in a period covering nearly three centuries, the sixth, fifth, and fourth, before our era. I shall only try to explain why the life and work of Socrates stand out as marking the central crisis or turning-point in that history. We speak of the pre-Socratics, then of Socrates, and finally of the Socratic philosophy elaborated by Plato and Aristotle. Why should the name of Socrates be used to describe the philosophy that came before him as well as the philosophy that came after?

Plato in one of his dialogues has made Socrates himself describe the revolution of thought he effected—how he turned philosophy from the study of external Nature to the study of man and of the purposes of human action in society. In the Phaedo, the conversation between Socrates and his friends on the day of his death reaches the question whether the soul is a thing of the sort that can begin and cease to exist. This question calls for a review of the explanations that had been given of the becoming and perishing of transitory things. Let me recall the substance of that famous passage.

We have considered the Ionian science of Nature—the germ from which all European science has since developed—as marking the achievement of an attitude of mind in which the object has been completely detached from the subject and can be contemplated by thought disengaged from the interests of action. The fruits of this attitude were the first systems of the world that can claim to be rational constructions of reality. We now come to the question, why they did not satisfy the expectations of Socrates. If the thought of these Ionians was genuinely philosophic, if they aimed at an entirely rational picture of the real, why did they disappoint a man whom the world has recognised as a great philosopher and who exalted the reason above all other faculties of man?

All our credible authorities—Plato, Xenophon, Aristotle—agree in asserting that Socrates, after his youthful disillusionment as to the methods and results of physical inquiry, never discussed such questions as the origin of the world. Xenophon adds some reasons. Did men of science imagine they understood human concerns so well that they could afford to neglect them for the study of things outside man's sphere and beyond his power of discovering the truth? They did not even agree among themselves, but contradicted one another on fundamental points. Did they hope, by studying the heavens, to control the weather; or were they content to know how the wind comes to blow and the rain to fall?

Socrates was one of that small number of adventurers who, from time to time, have enlarged the horizon of the human spirit. They have divined in our nature unsuspected powers which only they have as yet, in their own persons, brought to fulfilment. By living the truth they discovered they gave the world the only possible assurance that it is not an illusion. By definition, it is a truth beyond the comprehension of their contemporaries and countrymen. Conviction is slowly carried to posterity by the example of their lives, not by any record they bequeath in writing. For, with a few exceptions, they have not written books. They were wise, and knew that the letter is destined to kill much (though not all) of the life that the spirit has given. The only language they could use was inevitably open to misconstruction. A new range of truth can hardly be disclosed in words bearing the worn impress of familiar usage. Those who, by intimate contact, felt the force of their personality, have believed in them, more than in anything they said.

Only by a rare stroke of fortune has one or another of these pioneers of thought found a single disciple who could grasp his meaning well enough to perform the task of handing it on. Even so, there arises a curious dilemma, which can hardly be escaped. Unless this disciple is himself a man of genius, he is not likely to rise to the height of his argument.