From the time of Socrates on, the majority of Greeks, had they been asked what was the ultimate object of endeavour, or what made life worth living, would have answered, pleasure. But among professional philosophers such a definition of the supreme good met with little favour. Seeing very clearly that the standard of conduct must be social, and convinced that it must at the same time include the highest good of the individual, they found it impossible to believe that the two could be reconciled by encouraging each citizen in the unrestricted pursuit of his own private gratifications. Nor had such an idea as the greatest happiness of the greatest number ever risen above their horizon; although, from the necessities of life itself, they unconsciously assumed it in all their political discussions. The desire for pleasure was, however, too powerful a motive to be safely disregarded. Accordingly we find Socrates frequently appealing to it when no other argument was likely to be equally efficacious, Plato striving to make the private satisfaction of his citizens coincide with the demands of public duty, and Aristotle maintaining that this coincidence must spontaneously result from the consolidation of moral habits; the true test of a virtuous disposition being, in his opinion, the pleasure which accompanies its exercise. One of the companions of Socrates, Aristippus the Cyrenaean, a man who had cut himself loose from every political and domestic obligation, and who was remarkable for the versatility with which he adapted himself to the most varying circumstances, went still further. He boldly declared that pleasure was the sole end worth seeking, and on the strength of this doctrine came forward as the founder of a new philosophical school. According to his system, the _summum bonum_ was not the total amount of enjoyment secured in a lifetime, but the greatest single enjoyment that could be secured at any moment; and this principle was associated with an idealistic theory of perception, apparently suggested by Protagoras, but carrying his views much further. Our knowledge, said Aristippus, is strictly limited to phenomena; we are conscious of nothing beyond our own feelings; and we have no right to assume the existence of any objects by which they are caused. The study of natural science is therefore waste of time; our whole energies should be devoted to the interests of practical life.[123] Thus Greek humanism seemed to have found its appropriate sequel in hedonism, which, as an ethical theory, might quote in its favour both the dictates of immediate feeling and the sanction of public opinion.