nor pass away into that which is not. Further, the atoms are unlimited in size and number, and they are borne along in the whole universe in a vortex, and thereby generate all composite things — fire, water, air, earth ; for even these are conglomerations of given atoms. And it is because of their solidity that these atoms are impassive and unalterable. The sun and the moon have been composed of such smooth and spherical masses [i.e. atoms], and so also the soul, which is identical with reason. We see by virtue of the impact of images upon our eyes. All things happen by virtue of necessity, the vortex being the cause of the creation of all things, and this he calls necessity. The end of action is tranquillity, which is not identical with pleasure, as some by a false interpretation have understood, but a state in which the soul continues calm and strong, undisturbed by any fear or superstition or any other emotion. This he calls well-being and many other names. The qualities of things exist merely by convention ; in nature there is nothing but atoms and void space. These, then, are his opinions. Of his works Thrasylus has made an ordered catalogue, arranging them in fours, as he also arranged Plato's works. The ethical works are the following : I. Pythagoras. Of the Disposition of the Wise Man. Of those in Hades. Tritogeneia (so called because three things, on which all mortal life depends, come from her). II. Of Manly Excellence, or Of Virtue. Amalthea's Horn (the Horn of Plenty).