Every art and faculty contemplates certain things especially. When then it is itself of the same kind with the objects which it contemplates, it must of necessity contemplate itself also: but when it is of an unlike kind, it cannot contemplate itself. For instance, the shoemaker’s art is employed on skins, but itself is entirely distinct from the material of skins: for this reason it does not contemplate itself. Again, the grammarian’s art is employed about articulate speech; is then the art also articulate speech? By no means. For this reason it is not able to contemplate itself. Now reason, for what purpose has it been given by nature? For the right use of appearances. What is it then itself? A system of certain appearances. So by its nature it has the faculty of contemplating itself so. Again, sound sense, for the contemplation of what things does it belong to us? Good and evil, and things which are neither. What is it then itself? Good. And want of sense, what is it? Evil. Do you see then that good sense necessarily contemplates both itself and the opposite? For this reason it is the chief and the first work of a philosopher to examine appearances, and to distinguish them, and to admit none without examination. You see even in the matter of coin, in which our interest appears to be somewhat concerned, how we have invented an art, and how many means the assayer uses to try the value of coin, the sight, the touch, the smell, and lastly the hearing. He throws the coin down, and observes the sound, and he is not content with its sounding once, but through his great attention he becomes a musician. In like manner, where we think that to be mistaken and not to be mistaken make a great difference, there we apply great attention to discovering the things which can deceive. But in the matter of our miserable ruling faculty, yawn............