48 But, says some one, you in vain claim so much for Christ, when we now know, and have in past times known, of other gods both giving remedies to many who were sick, and healing the diseases and the infirmities of many men. I do not inquire, I do not demand, what god did so, or at what time; whom he relieved, or what shattered frame he restored to sound health: this only I long to hear, whether, without the addition of any substance— that is, of any medical application— he ordered diseases to fly away from men at a touch; whether he commanded and compelled the cause of ill health to be eradicated, and the bodies of the weak to return to their natural strength.
For it is known that Christ, either by applying His hand to the parts affected, or by the command of His voice only, opened the ears of the deaf, drove away blindness from the eyes, gave speech to the dumb, loosened the rigidity of the joints, gave the power of walking to the shrivelled,— was wont to heal by a word and by an order, leprosies, agues, dropsies, and all other kinds of ailments, which some fell power has willed that the bodies of men should endure. What act like these have all these gods done, by whom you allege that help has been brought to the sick and the imperilled?
For if they have at any time ordered, as is reported, either that medicine or a special diet be given to some, or that a draught be drunk off, or that the juices of plants and of blades be placed on that which causes uneasiness or have ordered that persons should walk, remain at rest, or abstain from something hurtful—and that this is no great matter, and deserves no great admiration, is evident, if you will attentively examine it— a similar mode of treatment is followed by physicians also, a creature earth-born and not relying on true science, but founding on a system of conjecture, and wavering in estimating probabilities.
Now there is no special merit in removing by remedies those ailments which affect men: the healing qualities belong to the drugs— not virtues inherent in him who applies them; and though it is praiseworthy to know by what medicine or by what method it may be suitable for persons to be treated, there is room for this credit being assigned to man, but not to the deity. For it is, at least, no discredit that he should have improved the health of man by things taken from without: it is a disgrace to a god that he is not able to effect it of himself, but that he gives soundness and safety only by the aid of external objects.
Source: Against the Heathen (New Advent)