I do not know, indeed, how he could conjoin things that do not admit of union, and which cannot exist together at the same time in human nature, in saying, as he did, that “the above treatise deserved to be treated both with pity and hatred.” For every one will admit that he who is the object of pity is not at the same moment an object of hatred, and that he who is the object of hatred is not at the same time a subject of pity. Celsus, moreover, says that it was not his purpose to refute such statements, because he thinks that their absurdity is evident to all, and that, even before offering any logical refutation, they will appear to be bad, and to merit both pity and hatred.
But we invite him who peruses this reply of ours to the charges of Celsus to have patience, and to listen to our sacred writings themselves, and, as far as possible, to form an opinion from their contents of the purpose of the writers, and of their consciences and disposition of mind; for he will discover that they are men who strenuously contend for what they uphold, and that some of them show that the history which they narrate is one which they have both seen and experienced, which was miraculous, and worthy of being recorded for the advantage of their future hearers.
Will any one indeed venture to say that it is not the source and fountain of all blessing (to men) to believe in the God of all things, and to perform all our actions with the view of pleasing Him in everything whatever, and not to entertain even a thought unpleasing to Him, seeing that not only our words and deeds, but our very thoughts, will be the subject of future judgment? And what other arguments would more effectually lead human nature to adopt a virtuous life, than the belief or opinion that the supreme God beholds all things, not only what is said and done, but even what is thought by us?
And let any one who likes compare any other system which at the same time converts and ameliorates, not merely one or two individuals, but, as far as in it lies, countless numbers, that by the comparison of both methods he may form a correct idea of the arguments which dispose to a virtuous life.
Source: Against Celsus (New Advent)