round bodies; and in like manner the soul is produced; and that the soul and the mind are identical: that we see by the falling of visions across our sight; and that everything that happens, happens of necessity. Motion, being the cause of the production of everything, which he calls necessity. The chief good he asserts to be cheerfulness; which, however, he does not consider the same as pleasure; as some people, who have misunderstood him, have fancied that he meant; but he understands by cheerfulness, a condition according to which the soul lives calmly and steadily, being disturbed by no fear, or superstition, or other passion. He calls this state εὐθυμία, and εὐεστὼ, and several other names. Everything which is made he looks upon as depending for its existence on opinion; but atoms and the vacuum he believes exist by nature. These were his principal opinions.
XIII. Of his books, Thrasylus has given a regular catalogue, in the same way that he has arranged the works of Plato, dividing them into four classes.
Now these are his ethical works. The Pythagoras; a treatise on the Disposition of the Wise Man; an essay on those in the Shades Below; the Tritogeneia (this is so called because from Minerva three things are derived which hold together all human affairs); a treatise on Manly Courage or Valour; the Horn of Amalthea; an essay on Cheerfulness; a volume of Ethical Commentaries. A treatise entitled, For Cheerfulness, (εὐεστὼ) is not found.
These are his writings on natural philosophy. The Great World (which Theophrastus asserts to be the work of Leucippus); the Little World; the Cosmography; a treatise on the Planets; the first book on Nature; two books on the Nature of Man, or on Flesh; an essay on the Mind; one on the Senses (some people join these two together in one volume, which they entitle, on the Soul); a treatise on Juices; one on Colours; one on the Different Figures; one