45 And as we read that he used food also, by which bodily existence is kept up, he has a large gullet, that he may gulp down the food sought for with gaping mouth; he has a belly to receive it, and a place where he may digest the flesh which he has eaten and devoured, that blood may be given to his body, and his strength recruited; he has also a draught, by which the filth is got rid of, freeing his body from a disagreeable burden. Whenever he changes his place, and prepares to pass from one region to another, he does not as a god fly secretly through the stars of heaven, and stand in a moment where something requires his presence, but, just as a dull animal of earth, he seeks a conveyance on which he may be borne; he avoids the waves of the sea; and that he may be safe and sound, he goes on board ship along with men; and that god of the common safety trusts himself to weak planks and to sheets of wood joined together.
We do not think that you can prove and show that that serpent was Aesculapius, unless you choose to bring forward this pretext, that you should say that the god changed himself into a snake, in order that he might be able to deceive men as to himself, who he was, or to see what men were. But if you say this, the inconsistency of your own statements will show how weak and feeble such a defence is. For if the god shunned being seen by men, he should not have chosen to be seen in the form of a serpent, since in any form whatever he was not to be other than himself, but always himself.
But if, on the other hand, he had been intent on allowing himself to be seen— he should not have refused to allow men's eyes to look on him — why did he not show himself such as he knew that he was in his own divine power? For this was preferable, and much better, and more befitting his august majesty, than to become a beast, and be changed into the likeness of a terrible animal, and afford room for objections, which cannot be decided, as to whether he was a true god, or something different and far removed from the exalted nature of deity.
Source: Against the Heathen (New Advent)