chief good, which contains all philosophy, and see whether Zeno has brought forward any reason for dissenting from the original discoverers and parents of it, as I may call them. While speaking, then, on this topic—although, Cato, this summit of goods, which contains all philosophy, has been carefully explained by you, and though you have told us what is considered so by the Stoics, and in what sense it is called so—yet I also will give my explanation, in order that we may see clearly, if we can, what new doctrine has been introduced into the question by Zeno. For as preceding philosophers, and Polemo most explicitly of all, had said that the chief good was to live according to nature, the Stoics say that three things are signified by these words: one, that a man should live exercising a knowledge of those things which happen by nature; and they say that this is the chief good of Zeno, who declares, as has been said by you, that it consists in living in a manner suitable to nature: the second meaning is much the same as if it were said that a man ought to live attending to all, or nearly all, the natural and intermediate duties. But this, when explained in this manner, is different from the former. For the former is right, which you called κατόρθωμα, and it happens to the wise man alone; but this is only a duty which is begun and not perfected, and this may happen to some who are far from being wise: the third is that a man should live, enjoying all things, or at least all the most important things which are according to nature; but this does not always depend on ourselves, for it is perfected both out of that kind of life which is bounded by virtue, and out of those things which are according to nature, and which are not in our own power.
But this chief good, which is understood in the third signification of the definition, and that life which is passed in conformity with that good, can happen to the wise man alone, because virtue is connected with it. And that summit of good, as we see it expressed by the Stoics themselves, was laid down by Xenocrates and by Aristotle; and so that first arrangement of the principles of nature, with which you also began, is explained by them in almost these very words.
VII. All nature desires to be a preserver of itself, in order that it may be both safe itself, and that it may be preserved in its kind. They say that for this end arts have been invented
