If a man of good natural disposition acquires Intelligence [as a whole], then he excels in conduct, and the disposition which previously only resembled Virtue, will now be Virtue in the true sense. Hence just as with the faculty of forming opinions [the calculative faculty] there are two qualities, Cleverness and Prudence, so also in the moral part of the soul there are two qualities, natural virtue and true Virtue; and true Virtue cannot exist without Prudence.

Now the soul of man is divided into two parts, one of which has a rational principle in itself, and the other, not having a rational principle in itself, is able to obey such a principle. And we call a man in any way good because he has the virtues of these two parts.

If there is any kind of animal which is female and has no male separate from it, it is possible that this may generate a young one from itself. No instance of this worthy of any credit has been observed up to the present at any rate, but one case in the class of fishes makes us hesitate. No male of the so-called erythrinus has ever yet been seen, but females, and specimens full of roe, have been seen. Of this, however, we have as yet no proof worthy of credit.

A man's happiness consists in the free exercise of his highest faculties.

We may assume the superiority ceteris paribus of the demonstration which derives from fewer postulates or hypotheses - in short, from fewer premises.

For well-being and health, again, the homestead should be airy in summer, and sunny in winter. A homestead possessing these qualities would be longer than it is deep; and its main front would face the south.

If you prove the cause, you at once prove the effect; and conversely nothing can exist without its cause.