_Cleanthes_ was born at Assos in the Troas, about 300 B.C.; he came to Athens at an early age, and became the pupil of Zeno, whom at his death he succeeded in his school. He differed from his master in regarding the soul as immortal, and approximated to the Cynics in denying that pleasure was agreeable to nature, or in any respect good. He died of voluntary starvation at the age of eighty. _Chrysippus_ was born B.C. 280, at Soli in Cilicia. He came at an early age to Athens, and became a pupil of Cleanthes; and among the later Stoics he was more regarded than either Zeno or Cleanthes. He died B.C. 207. His doctrines do not appear to have differed from those of Zeno; only that, from feeling the dangerous influence of the Epicurean principles, he endeavoured to popularize the Stoic ethics. _Epicurus_ was an Athenian of the Attic demos Gargettus, whence he is sometimes simply called the Gargettian. He was, however, born at Samos, B.C. 342, and did not come to Athens till the age of eighteen, when he found Xenocrates at the head of the Academy, and by some authors is said to have become his pupil, though he himself would not admit it (Cic. de Nat. Deor. i. 26). At the outbreak of the Samian war he crossed over to Colophon, where he collected a school. It is said that the first thing that excited him to the study of philosophy was the perusal of the works of Democritus while he resided at Colophon. From thence he went to Mitylene and Lampsacus, and B.C. 306 he returned to Athens, and finally established himself as a teacher of philosophy. His own life was that of a man of simple, pure, and temperate habits. He died of the stone, B.C. 270, and left Hermarchus of Mitylene as his successor in the management of his school. None of his works have come down to us. With regard to his philosophical system, in spite of his boast of being self-taught and having borrowed from no one, he clearly derived the chief part of his natural philosophy from Democritus, and of his moral philosophy from Aristippus and the Cyrenaics. He considered human happiness the end of all philosophy, and agreed with the Cyrenaics that pleasure constituted the greatest happiness; still this theory in his hands acquired a far loftier character; for pleasure, in his idea, was not a mere momentary and transitory sensation, but something lasting and imperishable, consisting in pure mental enjoyments, and in the freedom from pain and any other influence which could disturb man’s peace of mind. And the _summum bonum_, according to him, consisted in this peace of mind; which was based upon correct wisdom (φρόνησις).