It is with a certain eloquence, indeed, that he appears to advocate the cause of those who bear witness to the truth of Christianity by their death, in the following words: “And I do not maintain that if a man, who has adopted a system of good doctrine, is to incur danger from men on that account, he should either apostatize, or feign apostasy, or openly deny his opinions.” And he condemns those who, while holding the Christian views, either pretend that they do not, or deny them, saying that “he who holds a certain opinion ought not to feign recantation, or publicly disown it.”
And here Celsus must be convicted of self-contradiction. For from other treatises of his it is ascertained that he was an Epicurean; but here, because he thought that he could assail Christianity with better effect by not professing the opinions of Epicurus, he pretends that there is a something better in man than the earthly part of his nature, which is akin to God, and says that “they in whom this element, viz., the soul, is in a healthy condition, are ever seeking after their kindred nature, meaning God, and are ever desiring to hear something about Him, and to call it to remembrance.”
Observe now the insincerity of his character! Having said a little before, that “the man who had embraced a system of good doctrine ought not, even if exposed to danger on that account from men, to disavow it, or pretend that he had done so, nor yet openly disown it,” he now involves himself in all manner of contradictions. For he knew that if he acknowledged himself an Epicurean, he would not obtain any credit when accusing those who, in any degree, introduce the doctrine of Providence, and who place a God over the world. And we have heard that there were two individuals of the name of Celsus, both of whom were Epicureans; the earlier of the two having lived in the time of Nero, but this one in that of Adrian, and later.
Source: Against Celsus (New Advent)