text: This is what Aristo says; and I shall answer his arguments one by one. First, in opposition to what he says about one's obligation to remove that which blocks the eye and hinders the vision. I admit that such a person does not need precepts in order to see, but that he needs treatment for the curing of his eyesight and the getting rid of the hindrance that handicaps him. For it is Nature that gives us our eyesight; and he who removes obstacles restores to Nature her proper function. But Nature does not teach us our duty in every case. Again, if a man's cataract is cured, he cannot, immediately after his recovery, give back their eyesight to other men also; but when we are freed from evil we can free others also. There is no need of encouragement, or even of counsel, for the eye to be able to distinguish different colours; black and white can be differentiated without prompting from another. The mind, on the other hand, needs many precepts in order to see what it should do in life; although in eye-treatment also the physician not only accomplishes the cure, but gives advice into the bargain. He says: "There is no reason why you should at once expose your weak vision to a dangerous glare; begin with darkness, and then go into half-lights, and finally be more bold, accustoming yourself gradually to the bright light of day. There is no reason why you should study immediately after eating; there is no reason why you should impose hard tasks upon your eyes when they are swollen and inflamed; avoid winds and strong blasts of cold air that blow into your face," – and other suggestions of the same sort, which are just as valuable as drugs themselves. The physician's art supplements remedies by advice.