Vitae philosophorum

Zeno of Citium and Antipater, in their treatises De anima, and Posidonius define the soul as a warm breath; for by this we become animate and this enables us to move. Cleanthes indeed holds that all souls continue to exist until the general conflagration; but Chrysippus says that only the souls of the wise do so.[*](Cf. Aet. Plac. iv. 19. 4 (Arnim, ii. p. 140).)

They count eight parts of the soul: the five senses, the generative power in us, our power of speech, and that of reasoning. They hold that we see when the light between the visual organ and the object stretches in the form of a cone: so Chrysippus in the second book of his Physics and Apollodorus. The apex of the cone in the air is at the eye, the base at the object seen. Thus the thing seen is reported to us by the medium of the air stretching out towards it, as if by a stick.

We hear when the air between the sonant body and the organ of hearing suffers concussion, a vibration which spreads spherically and then forms waves and strikes upon the ears, just as the water in a reservoir forms wavy circles when a stone is thrown into it. Sleep is caused, they say, by the slackening of the tension in our senses, which affects the ruling part of

Semen is by them defined as that which is capable of generating offspring like the parent. And the human semen which is emitted by a human parent in a moist vehicle is mingled with parts of the soul, blended in the same ratio in which they are present in the parent.

Chrysippus in the second book of his Physics declares it to be in substance identical with vital breath or spirit. This, he thinks, can be seen from the seeds cast into the earth, which, if kept till they are old, do not germinate, plainly because their fertility has evaporated. Sphaerus and his followers also maintain that semen derives its origin from the whole of the body; at all events every part of the body can be reproduced from it. That of the female is according to them sterile, being, as Sphaerus says, without tension, scanty, and watery. By ruling part of the soul is meant that which is most truly soul proper, in which arise presentations and impulses and from which issues rational speech. And it has its seat in the heart.

Such is the summary of their Physics which I have deemed adequate, my aim being to preserve a due proportion in my work. But the points on which certain of the Stoics differed from the rest are the following.

Ariston the Bald, of Chios, who was also called the Siren, declared the end of action to be a life of perfect indifference to everything which is neither virtue nor vice; recognizing no distinction whatever