Greek polemical writer against Christianity; flourished in the second century. He was the first pagan who denounced Christianity, and in his work, "The True Word" (Λόγος 'ΛληΘής), he attempted not only to refute but to ridicule the doctrines of Christianity. Although the work has been lost, large fragments of it are preserved in the apology of Christianity ("Contra Celsum," in eight books) written by Origen in answer to Celsus. An attempt was recently made by Keim and Muth to reconstruct the original from these fragments. Origen was not clear as to the person of Celsus; he mentions two Epicureans by that name, one of whom was said to have lived under Nero and the other under Hadrian; and it was against the latter that he directed his polemic. In designating his opponent by the opprobrious epithet of "Epicurean," Origen was misled by his prejudice; for Celsus, according to his own teachings, was an eclectic, following Plato and perhaps also Philo. Moreover, he must have lived after Hadrian's time, probably flourishing about 180 under Marcus Aurelius (161-180), since he mentions the Marcionites and the Marcellians. Lucian, who also denounced Christianity, dedicated to him his "Alexander, the Lying Prophet" ("Alex." xxi.).
In the first book of Celsus from which Origen took his extracts, a Jew, introduced by Celsus, addresses Jesus; in the second book, the Jew addresses his Jewish coreligionists who have embraced Christianity; and in the remaining six books Celsus speaks in his own person. All this shows, as Mosheim says, that Celsus mingled with the Jews, getting from them the story of the life and passion of Jesus. Yet the Jew introduced knew so little about his own religion as to describe it often incorrectly; hence his introduction in the work is merely a rhetorical device, and Celsus himself is the speaker, promulgating opinions which he had heard or learned from Jews. Whether he reproduced mere verbal assertions of the Jews (compare Origen, "Contra Celsum," vi. § 27, and Justin, "Dial. cum Tryph." pp. 10, 17, 108), or information from written Jewish sources, can hardly be determined. Keim believes that Tertullian ("De Spect." xxx.) had a written Jewish polemical work before him; but it is certainly wrong to assume that Celsus used the "Toledot Yeshu."
Celsus was by no means friendly to the Jews, regarding them as slaves escaped from Egypt. He denounced their history, especially that contained in Genesis, as foolish fables (iv. 5, § 2), affirming that sensible Jews and Christians look upon these things as allegories. He knew the divine names "Adonai" and "Sabaoth," the rite of circumcision, and the command against eating pork; and he ridiculed these and similar laws. Although understanding why the Jews should cling to their own laws, he thought Christians foolish for renouncing Hellenism in order to become converts to a false doctrine. He compared the disputes of the Jews and Christians about the Messiah with the dispute about the shadow of the ass (iii. 1, § 2), and asked whether Moses or Jesus was right, since the latter countermanded what the former had ordained.
It has been assumed that Celsus' work contained material not to be found elsewhere; but he knows no more than is found in the Gospels, as has been proved. All beyond this is merely an addition to what has been called the Jesus myths.
Yet there are connections between Celsus and Judaism that must be emphasized; e.g., he asserts that Jesus was the illegitimate son of a certain Panthera, and, again, that he had been a servant in Egypt, not when a child, as according to the New Testament, but when he was grown, and that he learned there the secret arts (i. 9, § 7). These statements are frequently identical with those of the Talmud. Celsus might have heard this from the Jews; he makes his Jew say that he could tell more about Jesus if he chose. Origen, however, rightly explains this phrase as a rhetorical device (ii. 3, § 1). Celsus agreed with the Jews in the chief points of their controversy with Christians, denying the divinity of Jesus, declaring all the marvelous stories about him to be fables similar to those of Greek mythology, and saying that the Jews were right in refusing to accept Jesus, especially as he was betrayed even by his own disciples, and left helpless into the hands of his enemies.
Origen had no single historic fact to oppose to Celsus' assertions; he too knew only what the Gospels recount, but he interpreted them as a faithful Christian, and explained allegorically even the difficult passages in the Old Testament. Celsus gave all the ideas on miracles, angelology, and demonology current at his time even among the Jews; so that his treatise is important also for the study of Judaism.