Theodorus the Atheist, of Cyrene, was a Cyrenaic school philosopher and one of the well-known philosophers of the ancient time. He lived in Alexandria and Greece before finishing his days in his native Cyrene region. As a Cyrenaic philosopher, he taught that the aim of life was to achieve happiness and escape sorrow, and that wisdom resulted in the former as well as ignorance in the latter. Yet his supposed conservatism was his primary claim to fame. He was generally called the atheist by ancient scholars. Theodorus was a pupil of Aristippus the Younger, the elder's brother and Aristippus, who was more celebrated. He saw a number of philosophers 'lectures beside Aristippus; including Anniceris, and Dionysius the dialectician, Zeno of Citium, and Pyrrho. He was banished from Cyrene, but for what cause it is not stated; and it is from his saying recorded on this occasion, "Men of Cyrene, you do ill in banishing me from Libya to Greece, as well as from being a disciple of Aristippus, that it is inferred that he was a native of Cyrene. There is no related account of his subsequent history; but his anecdotes indicate that he was in Athens. Nevertheless, Demetrius Phalereus 'influence allegedly protected him; and this event will thus possibly be located at Athens, 317–307 BC, within the ten years of Demetrius' rule. Since Theodorus was exiled from Athens and was later in Ptolemy's service in Egypt, it is not unlikely that he joined Demetrius's overthrow and exile. The account cited by Diogenes Laërtius of Amphicrates of Athens, that he was condemned to drink hemlock and so died, is beyond doubt a error. While at Ptolemy's command, Theodorus was sent to Lysimachus on an ambassador, whom he insulted by the expression of his remarks. Several ancient authors praised one reaction he made to a crucifixion challenge that Lysimachus had used. He evidently returned from the Lysimachus court or camp to that of Ptolemy. We also read about his visit to Corinth with a number of his followers, but during his stay in Athens this was probably just a brief visit. He long returned to Cyrene, and stayed there, says Diogenes Laërtius, with Ptolemy's stepson Magas, who ruled Cyrene as viceroy for fifty years, then as king. Theodorus's days at Cyrene presumably ended. Various characteristic anecdotes of Theodorus are preserved from which he appears to have been a man of keen and ready wit. Theodorus was the founder of a church, called Theodoreans after him. Theodorus 'views, as can be learned from Diogenes Laërtius' perplexed comment, were of the Cyrenaic school. He explained that the true end of human life is to attain happiness and escape sorrow, and that wisdom is the former, and ignorance is the latter. He has described the good as prudence and fairness, and the bad as the opposite. Pleasure and pain were nevertheless oblivious. He made fun of friendship and loyalty, and said his country was the universe. He taught that nothing in stealing, treason, or sacrilege was necessarily disgraceful if one defied public opinion, which had been established by fools 'permission. They blamed Theodorus for atheism. He has excluded all views supporting the gods, Laërtius claims, but some opponents question that he was an atheist or merely denying the existence of common religion deities. The accusation of atheism is backed by Atheus 'popular classification, by the authority of Cicero, Laërtius, Pseudo-Plutarch, Sextus Empiricus, and some Christian writers; although others talk of him as denying traditional theology alone. He wrote other works on his sect's teachings as well as on other topics according to the Suda.