But we have something more to say to Celsus, when he declares that “the soul is the work of God, and that the nature of body is different,” and puts forward such an opinion not only without proof, but even without clearly defining his meaning; for he did not make it evident whether he meant that every soul is the work of God, or only the rational soul. This, then, is what we have to say: If every soul is the work of God, it is manifest that those of the meanest irrational animals are God's work, so that the nature of all bodies is different from that of the soul.
He appears, however, in what follows, where he says that “irrational animals are more beloved by God than we, and have a purer knowledge of divinity,” to maintain that not only is the soul of man, but in a much greater degree that of irrational animals, the work of God; for this follows from their being said to be more beloved by God than we. Now if the rational soul alone be the work of God, then, in the first place, he did not clearly indicate that such was his opinion; and in the second place, this deduction follows from his indefinite language regarding the soul— viz., whether not every one, but only the rational, is the work of God— that neither is the nature of all bodies different (from the soul).
But if the nature of all bodies be not different, although the body of each animal correspond to its soul, it is evident that the body of that animal whose soul was the work of God, would differ from the body of that animal in which dwells a soul which was not the work of God. And so the assertion will be false, that there is no difference between the body of a bat, or of a worm, or of a frog, and that of a man.
Source: Against Celsus (New Advent)