CELSUS. - 2nd-century philosopher, author of writings against Christianity. The person, work, and thought of C. are known to us only from the refutation made of them by Origen (v.) in the Contra Celsum. A Platonic philosopher, he was identified by some, seemingly wrongly, with the namesake follower of the Epicurean school, author of the Κατά μέγων ("Against the Magicians"), a friend of Lucian. He wrote a work against the Christians, probably in two books (Origen, op. cit., IV, 36), the Ἀληθής λόγος ("The True Doctrine"). This work was preserved for us in the aforementioned refutation by Origen, according to Neumann at least to the extent of 9/10, of which about 3/4 in literal text; Glöckner thinks that only at the beginning of the refutation did Origen fail to reproduce the text in full, whereas in all the rest he would have omitted only repetitions and insignificant details. It was probably composed in Egypt between 178-80.
It is the first wide-ranging writing of the anti-Christian polemic, in which the various already known motifs are arranged, developed, and augmented with new material. C. attacks Christianity armed with a good knowledge of the philosophical currents of the time, drawing willingly, besides on Platonism, on Epicurean doctrine. He also knows the Bible, various apocrypha, and early apologetic literature. He is informed about the conditions of the Christians, about orthodox and heretical doctrines, especially Gnostic ones. He accuses the Christians of ignorance, obscurantism, and fanaticism; he regards the Old Testament as a fabric of anthropomorphic fables, Jesus as a charlatan powerless to save himself, abandoned by his disciples; he considers the incarnation absurd; he denies the value of miracles and prophecies; he reproaches the Christians for their divisions; he rejects the Resurrection; he asserts that Christ read Plato, from whom the Christians derived much; he concludes by inviting the Christians to take their place again in social life in order to present a united front with the pagans against the barbarian danger.
Not without interest in itself for its acumen and polemical liveliness, the work is important, above all historically, as a document of the pagan mentality in the face of Christianity. It influenced particularly the anti-Christian polemic of Neoplatonism; Hierocles drew inspiration from it, even in the title, in the Λόγοι φιλαλήθεις. Certain attitudes of C. persist even in modern rationalism.