21 R. We have pain of body left, which perhaps moves you of its proper force. A. Nor indeed do I grievously dread even that for any other reason than that it impedes me in my research. For although of late I have been grievously tormented with attacks of toothache, so that I was not suffered to revolve anything in my mind except such things as I have been engaged in learning; while, as the whole intensity of my mind was requisite for new advances, I was entirely restrained from making these: yet it seemed to me, that if the essential refulgence of Truth would disclose itself to me, I should either not have felt that pain, or certainly would have made no account of it.
But although I have never had anything severer to bear, yet, often reflecting how much severer the pains are which I might have to bear, I am sometimes forced to agree with Cornelius Celsus, who says that the supreme good is wisdom, and the supreme evil bodily pain. For since, says he, we are composed of two parts, namely, mind and body, of which the former part, the mind, is the better, the body the worse; the highest good is the best of the better part, and the chiefest evil the worst of the inferior; now the best thing in the mind is wisdom, and the worst thing in the body is pain.
It is concluded, therefore, and as I fancy, most justly, that the chief good of man is to be wise, and his chief evil, to suffer pain. R. We will consider this later. For perchance Wisdom herself, towards which we strive, will bring us to be of another mind. But if she should show this to be true, we will then not hesitate to adhere to this your present judgment concerning the highest good and the deepest ill.
Source: Soliloquies (New Advent)