In his natural philosophy he embraced the atomic theories of Democritus and Diagoras, carrying them even further than they themselves had done, to such a degree that he drew upon himself the reproach of Atheism. He regarded the Gods themselves as consisting of atoms, and our notions of them as based upon the images (εἴδωλα) which are reflected from them, and so pass into our minds. And he believed that they exercised no influence whatever on the world, or on the actions or fortunes of man. _Theodorus_ was a native of Cyrene, who flourished about B.C. 320. He was of the Cyrenaic sect, and the founder of that branch of it which was called after him, the Theodorean; though we scarcely know in what his doctrines differed from those of Aristippus, unless they were, if possible, of a still more lax character. He taught, for instance, that there was nothing really wrong or disgraceful in theft, adultery, or sacrilege; but that they were branded by public opinion to restrain fools. He is also reproved with utter atheism; and Cicero classes him with Diagoras, as a man who utterly denied the existence of any Gods at all. _Pyrrho_ was a contemporary of Alexander the Great, whose expedition into Asia he joined. He appears, as far as his philosophy went, to have been an universal sceptic. He impeached, however, none of the chief principles of morality, but, regarding Socrates as his model, directed all his endeavours towards the production in his pupils of a firm well-regulated moral character. _Crantor_ was a native of Soli in Cilicia; we do not know when he was born or when he died, but he came to Athens before B.C. 315. He was the first of Plato’s followers who wrote commentaries on the works of his master. He died of dropsy, and left Arcesilaus his heir. _Arcesilaus_, or _Arcesilas_, flourished about B.C. 280; he was born at Pitane, but came to Athens and became the pupil of Theophrastus and of Crantor, and afterwards of some of the more sceptical philosophers. On the death of Crantor he succeeded to the chair of the Academy, in the doctrines of which he made so many innovations that he is called the founder of the New Academy. What his peculiar views were is, however, a matter of great uncertainty. Some give him the credit of having restored the doctrines of Plato in an uncorrupted form; while, according to Cicero, on the other hand, (Acad. i. 12,) he summed up all his opinions in the statement that he knew nothing, not even his own ignorance. He, and the New Academy, do not, however, seem to have doubted the existence of truth in itself, but only the capacity of man for arriving at the knowledge of it.