Into this world of thought came Socrates, the Gadfly of the Athenians (469-399 BC). His active mind was attracted early on by the exciting physical theories of his time, but later his passionate concern for humanity led him to abandon them as barren and devote himself to the defense of moral standards. He was convinced that ‘justice’ or ‘courage’ were realities. In any case, men used the words, so they ought to be able to say what they meant. He believed, moreover, that a knowledge of the true nature of goodness would inevitably make men seek it. The sole cause of wrongdoing was ignorance. The activities of this ‘gadfly’ (as he liked to call himself), in stirring up the minds and consciences of the Athenians were so distasteful to them that they brought him to trial and executed him. His simple moral outlook faced his successors with some intractable philosophical problems. Is there such a thing as goodness per se, considering different societies may have quite different conceptions of it? Can we know what it is? If we do, is it true that we will always seek it?
His pupil Plato (427-347), with a more many-sided intellect, set himself to answer these questions, the real and ideal worlds. There is a transcendent world of ‘forms’ (often called ‘ideas’ from the Greek word idea, but not ideas in our sense of mere concepts in the human mind), which are eternal and perfect entities serving as models for the passing and imperfect manifestations of truth in our world. Plato had been deeply impressed by the timeless world of mathematics revealed by the Pythagoreans and he applied its standards to the ethical and physical spheres. He also owes to the Pythagoreans his explanation of our knowledge of the ‘forms’. In the other world, between incarnations, we have been face-to-face with them and by intellectual and moral discipline we may ‘recollect’ that vision.
Psychologically, he elaborated Socrates’ simple ‘knowledge is virtue’ by a tripartite division of the soul into appetitive, spirited, or impulsive and rational parts. According as one or other of these parts is strongest in him, the eros (desire, libido) of every man will be directed more into the channels of material gain, honour and ambition, or philosophy (knowledge and goodness). This psychology is at the root of the aristocratic and authoritarian political system expounded in the Republic, with its strict class divisions; for to Plato it seemed obvious that only the philosophic type should be given the reins of government, defense should be entrusted to the spirited and those in whom the appetitive side was strongest were the natural producers and traders of wealth.
In his later years, Plato devoted more attention to problems of logic and the theory of knowledge and his work in these fields attracts much attention today, when these problems are in the forefront of philosophers’ interests. But though he saw the difficulties in the doctrine of ‘forms’, he never abandoned it and in the Timaeus he constructed an imaginative world-picture, including the origin of the universe and living beings and a detailed consideration of the bodily as well as psychical functions of mankind, which was entirely based on his two-world theory. Nor must one forget the poetry of the great myths about the adventures of the soul in the other world with which several of his dialogues close. The dialogues defy classification. They are a unique and inimitable blend of philosophical discussion, religious feeling, poetry and dramatic characterization.
Aristotle (384-322) was for twenty years a member of Plato’s Academy and this left an indelible impression on his mind; but his philosophical temperament was very different from Plato’s, a spirit of research. Born at Stagira in the north of Greece, he was brought up in the semi-Greek court of Philip of Macedon, to whom his father was court physician. The medical schools of Greece were closely linked with the philosophy and science of their time, but introduced into them a valuable note of empiricism. They distrusted vague generalizations and broad intellectual constructions, preferring to base their conclusions (as a doctor must) on the meticulous observation of individual cases. Of this the great Hippocratic Corpus, a still extant collection of medical writings from the 5th century onwards, is ample witness. The craft was handed on from father to son, so we may be certain that for Aristotle this approach to science was in his early upbringing as well as his ancestry. His own patient collection of scientific data, notably in zoology, is proof that he found it congenial and much in his philosophy explicable by the conflict between this empirical instinct and his Platonic training.
He retained the conception of form, as opposed to matter, as the determinative factor or ‘essence’ of things, but decisively abandoned belief in its existence beyond our world. Forms exist only in the sensible objects. Everything in nature, animal or plant, has an urge (dynamis) to realize its proper form, exemplified for it in its parent, so far as the limitations of matter allow. This impulse is activated by the one existing pure form, which is not, like a Platonic ‘idea’, the form of anything else, but God. God is perfect and therefore does not move or change in any way. He is unadulterated intellect, spending his life in eternal self-contemplation. At the same time, he is the Unmoved Mover or ultimate cause of all development in the natural world, for the mere existence of his perfection fills all nature with the desire to emulate it. (He did not create the world, for Aristotle believed it to have existed from all time.)
By his division of existence into potential and actual, Aristotle gave the final answer to the dilemma of Parmenides. There is such a thing as becoming, or change from one state to another, although as Parmenides said, it cannot proceed from not-being to being. What is not x is not non-existent, but simply at the moment not x and may have the dynamis of becoming x. In all this Aristotle was greatly indebted to the analysis of the different senses of being, which had been carried out by Plato.
In his writings on ethics and politics Aristotle was nearer to the Sophists than to Plato. There is no single ‘good’ over and above all other goods; what is good differs for different people or circumstances. Conduct is taken out of the sphere of philosophical knowledge, whose subject-matter must conform to permanent laws and confined to the contingent. Its regulation becomes a matter of practical good sense, almost of knack, or flair. On this basis, Aristotle worked out his doctrine of each separate virtue as a mean between two extremes. As to the exact point on the scale between, say, foolhardiness and cowardice at which true courage lay, he could only say it is “where the man of practical wisdom would put it.” Conforming to his scientific outlook, his writings on political theory were based on a collection of descriptions of no less than 158 different Greek constitutions amassed by himself and his pupils. This invaluable collection of historical material was entirely lost until the Constitution of Athens, written by Aristotle himself, turned up on a papyrus, in the sands of Egypt in 1890.
By the introduction of symbols Aristotle was the first to evolve a system of purely formal logic. This was based entirely on the syllogism, the varieties of which he classified exhaustively. (At its simplest a syllogism states a general rule—the major premise—, specifies a particular case as coming under that rule—the minor premise—, and draws the conclusion: e.g. “All animals are mortal; men are animals; therefore men are mortal’.) All logic in its formal aspect, even induction (the argument from particular cases to general laws), was reduced to syllogistic form. The system had immense influence through the Middle Ages and it was only in the 20th century that the ‘traditional logic’ based on Aristotle was substantially modified.