But I am very far from approving this conduct of yours, that when you have proved, as you imagine, that thatalone is good which is honourable, then say again that it is necessary that beginnings should be put forward which are suitable and adapted to nature; by a selection from which virtue might be called into existence. For virtue ought not to have been stated to consist in selection, so that that very thing which was itself the chief good, was to acquire something besides itself; for all things which are to be taken, or chosen, or desired, ought to exist in the chief good, so that he who has attained that may want nothing more. Do you not see how evident it is to those men whose chief good consists in pleasure, what they ought to do and what they ought not?so that no one of them doubts what all their duties ought to regard, what they ought to pursue, or avoid. Let this, then, be the chief good which is now defended by me; it will be evident in a moment what are the necessary duties and actions. But you, who set before yourselves another end except what is right and honourable, will not be able to find out where your principle of duty and action is to originate.
Therefore you are all of you seeking for this, and so are those who say that they pursue whatever comes into their mind and occurs to them; and you return to nature. But nature will fairly reply to you, that it is not true that the chief happiness of life is to be sought in another quarter, but the principles of action in herself: for that there is one system only, in which both the principles of action and the chief good too is contained; and that, as the opinion of Aristo is exploded, when he says that one thing does not differ from another, and that there is nothing except virtue and vice in which there was any difference whatever; so, too, Zeno was in the wrong, who affirmed that there was no influence in anything, except virtue or vice, of the very least power to assist in the attainment of the chief good: and as that had no influence on making life happy, but only in creating a desire for things, he said that there was some power of attraction in them: just as if this desire had no reference to the acquisition of the chief good. But what can be less consistent than what they say, namely, that when they have obtained the knowledge of the chief good they then return to nature, in order to seek in it the principle of action, that is to say, of duty? For it is not the principle of action or duty which impels them to desire those things which areaccording to nature; but desire and action are both set in motion by those things.