Basilides was one of the greatest and most famous of the Gnostics. Irenæus (I. 24) and the early Compendium of Hippolytus (now lost, but used together with Irenæus’ work by Epiphanius in his treatise against heresies) described a form of Basilidianism which was not the original, but a later corruption of the system. On the other hand, Clement of Alexandria surely, and Hippolytus, in the fuller account in his Philosoph. (VII. 2 sq.), probably drew their knowledge of the system directly from Basilides’ own work, the Exegetica, and hence represent the form of doctrine taught by Basilides himself,—a form differing greatly from the later corruptions of it which Irenæus discusses. This system was very profound, and bore in many respects a lofty character. Basilides had apparently few followers (his son Isidore is the only prominent one known to us); and though his system created a great impression at the start,—so much so that his name always remained one of the most famous of Gnostic names,—it had little vitality, and soon died out or was corrupted beyond recognition. He was mentioned of course in all the general works against heresies written by the Fathers, but no one seems to have composed an especial refutation of his system except Agrippa Castor, to whom Eusebius refers. Irenæus informs us that he taught at Alexandria, Hippolytus (VII. 15) mentions simply Egypt, while Epiphanius (XXI. 1) names various Egyptian cities in which he labored, but it is evident that he is only enumerating places in which there were Basilidians in his time. It is not certain whether he is to be identified with the Basilides who is mentioned in the Acts of Archelaus as preaching in Persia. For an excellent account of Basilides and his system, see the article by Hort in the Dict. of Christ. Biog.; and in addition to the works of Neander, Baur, and Lipsius on Gnosticism in general, see especially Uhlhorn’s Das Basilidianische System, Göttingen, 1855.