XIII. From Plato, therefore, all my discourse shall be deduced, as if from some sacred and hallowed fountain. Whence can I, then, more properly begin than from Nature, the parent of all? For whatsoever she produces (I am not speaking only of animals, but even of those things which have sprung from the earth in such a manner as to rest on their own roots) she designed it to be perfect in its respective kind. So that among trees and vines, and those lower plants and trees which cannot advance themselves high above the earth, some are evergreen, others are stripped of their leaves in winter, and, warmed by the spring season, put them out afresh, and there are none of them but what are so quickened by a certain interior motion, and their own seeds enclosed in every one, so as to yield flowers, fruit, or berries, that all may have every perfection that belongs to it; provided no violence prevents it. But the force of Nature itself may be more easily discovered in animals, as she has bestowed sense on them. For some animals she has taught to swim, and designed to be inhabitants of the water; others she has enabled to fly, and has willed that they should enjoy the boundless air; some others she has made to creep, others to walk. Again, of these very animals, some are solitary, some gregarious, some wild, others tame, some hidden and buried beneath the earth, and every one of these maintains the law of nature, confining itself to what was bestowed on it, and unable to change its manner of life. And as every animal has from nature something that distinguishes it, which every one maintains and never quits; so man has something far more excellent, though everything is said to be excellent by comparison. But the human mind, being derived from the divine reason, can be compared with nothing but with the Deity itself, if I may be allowed the expression. This, then, if it is improved, and when its perception is so preserved as not to be blinded by errors, becomes a perfect understanding, that is to say, absolute reason, which is the very same as virtue. And if everything is happy which wants nothing, and is complete and perfect in its kind, and that is the peculiar lot of virtue, certainly all who are possessed of virtue are happy. And in this I agree with Brutus, and also with Aristotle, Xenocrates, Speusippus, Polemon.