to pursue the opinions of the ancients with the greatest care; and he shows that they coincided with the doctrines of Aristotle and Polemo. VI. My young friend Lucius, therefore, acts prudently when he wishes chiefly to be instructed about the chief good; for when this point is once settled in philosophy, everything is settled. For in other matters, if anything is passed over, or if we are ignorant of anything, the inconvenience thus produced is no greater than the importance the matter is of in which the omission has taken place; but if one is ignorant of what is the chief good, one must necessarily be ignorant of the true principles of life; and from this ignorance such great errors ensue that they cannot tell to what port to betake themselves. But when one has acquired a knowledge of the chief ends,—when one knows what is the chief good and the chief evil,—then a proper path of life, and a proper regulation of all the duties of life, is found out. There is, therefore, an object to which everything may be referred; from which a system of living happily, which is what every one desires, may be discovered and adopted. But since there is a great division of opinion as to what that consists in, we had better employ the division of Carneades, which our friend Antiochus prefers, and usually adopts. He therefore saw not only how many different opinions of philosophers on the subject of the chief good there were, but how many there could be. Accordingly, he asserted that there was no art which proceeded from itself; for, in truth, that which is comprehended by an art is always exterior to the art. There is no need of prolonging this argument by adducing instances; for it is evident that no art is conversant about itself, but that the art itself is one thing, and the object which is proposed to be attained by the art another. Since, therefore, prudence is the art of living, just as medicine is of health, or steering of navigation, it follows unavoidably that that also must have been established by, and must proceed from, something else. But it is agreed among almost all people, that that object with which prudence is conversant, and which it wishes to arrive at, ought to be fitted and suited to nature, and to be of such a character as by itself to invite and attract that desire of the mind which the Greeks call ὁρμή. But as to what it is which causes this excitement, and which is so greatly desired by nature from its first existence, it is not agreed; and, indeed, there is a great dissension on the subject among philosophers whenever the chief good is the subject of investigation: for the source of this whole question which is agitated as to the chief good and evil, when men inquire what is the extreme and highest point of either, must be traced back, and in that will be found the primitive inducements of nature; and when it is found, then the whole discussion about the chief good and evil proceeds from it as from a spring.