From Aristotle it is necessary to turn to Zeno, for the Peripatetics and Stoics stand in parallel lines. The social conditions existing in Greece at the time of Epicurus may in some degree palliate his sentiments, but virtue and honour will make themselves felt at last. Stoicism soon appeared as the antagonist of Epicureanism, and Epicurus found in Zeno of Citium a rival. The passage from Epicurus to Zeno is the passage from sensual gratification to self-control. The biography of Zeno may be dismissed in a few words. Born about B.C. 300, he spent the early part of his life in the vocation of his father, who was a merchant, but, by a fortunate shipwreck, happily losing his goods during a voyage he was making to Athens, he turned to philosophy for consolation. Though he had heretofore been somewhat acquainted with the doctrines of Socrates, he became a disciple of the Cynics, subsequently studying in the Megaric school, and then making himself acquainted with Platonism. After twenty years of preparation, he opened a school in the stoa or porch in Athens, from which his doctrine and disciples have received their name. He presided over his school for fifty-eight years, numbering many eminent men among his disciples. When nearly a hundred years old he chanced to fall and break his finger, and, receiving this as an admonition that his time was accomplished, he forthwith strangled himself. The Athenians erected to his memory a statue of brass. His doctrines long survived him, and, in times when there was no other consolation for man, offered a support in their hour of trial, and an unwavering guide in the vicissitudes of life, not only to many illustrious Greeks, but also to some of the great philosophers, statesmen, generals, and emperors of Rome. [Sidenote: Intention of Stoicism.] It was the intention of Zeno to substitute for the visionary speculations of Platonism a system directed to the daily practices of life, and hence dealing chiefly with morals. To make men virtuous was his aim. But this is essentially connected with knowledge, for Zeno was persuaded that if we only know what is good we shall be certain to practise it. He therefore rejected Plato's fancies of Ideas and Reminiscences, leaning to the common-sense doctrines of Aristotle, to whom he approached in many details. With him Sense furnishes the data of knowledge, and Reason combines them: the soul being modified by external things, and modifying them in return, he believed that the mind is at first, as it were, a blank tablet, on which sensation writes marks, and that the distinctness of sensuous impressions is the criterion of their truth. The changes thus produced in the soul constitute ideas; but, with a prophetic inspiration, he complained that man will never know the true essence of things. [Sidenote: The Physics of Zeno.]