CHRYSIPPUS (c. 280-206 b.c.), one of the greatest of the Stoics, was born probably in 280 B.C., at Soli, in Cilicia. Being robbed of his property, he visited Athens, and attended the lectures, possibly of Zeno, and certainly of Cleanthes. The latter he succeeded as recognized chief of the school. He is also said to have been instructed in the doctrines of the Middle Academy by Arcesilaus and Lacydes. Chrysippus was the author of a prodigious number of works, which, though extremely prolix and disfigured by great obscurity and carelessness of style and language, were distinguished by extensive learning and considerable acuteness. But nothing has come down to us except small fragments, and from these it is difficult to discover what doctrines are originally due to Chrysippus. We know, however, that he made considerable emendations on the theory of Zeno and Cleanthes. With regard to the relation of moral to physical science, he reversed their conclusion, adopting the view, which from that time became characteristic of Stoicism, that, as the sole aim of philosophy is to discover man’s duty, ethics is the only science that is of real importance in itself, while physics is to be regarded merely as an aid to its study. He improved on the crude theory of perception which had been held by his predecessors, who compared the action of the object on the mind to that of the seal on the wax, arguing that this would do away with the possibility of the simultaneous perception of more than one object, and denying that the mental modification resembles the object. He also finally determined the Stoical theory of the criterion of truth, which, according to him, is irresistible conviction. Much attention was paid by Chrysippus to formal logic. He held that the hypothetical syllogism is ...