Moreover, as we have already said that for God to desire anything unbecoming Himself would be destructive of His existence as Deity, we will add that if man, agreeably to the wickedness of his nature, should desire anything that is abominable, God cannot grant it. And now it is from no spirit of contention that we answer the assertions of Celsus; but it is in the spirit of truth that we investigate them, as assenting to his view that “He is the God, not of inordinate desires, nor of error and disorder, but of a nature just and upright,” because He is the source of all that is good.
And that He is able to provide an eternal life for the soul we acknowledge; and that He possesses not only the “power,” but the “will.” In view, therefore, of these considerations, we are not at all distressed by the assertion of Heraclitus, adopted by Celsus, that “dead bodies are to be cast out as more worthless than dung;” and yet, with reference even to this, one might say that dung, indeed, ought to be cast out, while the dead bodies of men, on account of the soul by which they were inhabited, especially if it had been virtuous, ought not to be cast out.
For, in harmony with those laws which are based upon the principles of equity, bodies are deemed worthy of sepulture, with the honours accorded on such occasions, that no insult, so far as can be helped, may be offered to the soul which dwelt within, by casting forth the body (after the soul has departed) like that of the animals. Let it not then be held, contrary to reason, that it is the will of God to declare that the grain of wheat is not immortal, but the stalk which springs from it, while the body which is sown in corruption is not, but that which is raised by Him in incorruption.
But according to Celsus, God Himself is the reason of all things, while according to our view it is His Son, of whom we say in philosophic language, “In the beginning was the Word, and the Word was with God, and the Word was God;” while in our judgment also, God cannot do anything which is contrary to reason, or contrary to Himself.
Source: Against Celsus (New Advent)