Allowing that many of these statements are natural consequences of the principles of Epicurus, the distinction between a rational and an irrational soul must, nevertheless, at first sight seem strange in a system so thoroughly materialistic as was that of the Epicureans. And yet this distinction is not stranger than the corresponding parts of the Stoic teaching. If the Stoic views may be referred to the distinction which they drew in morals between the senses and the reason, not less are the Epicurean ethics marked by the same contrast between the general and the sensuous side of the mind. Hence Epicurus shares the Stoic belief in an ethereal origin of the human race; [1228] and although this belief as at first expressed only implies that man, like other living beings, is composed of ethereal elements, yet there is connected with it the distinction already discussed in the case of the Stoics between the higher and the lower parts of man, which ultimately comes to be simply another mode of expressing the difference between mind and matter. [(3) Sensation.] Among the phenomena of the soul’s life sensation is made to harmonise with the general principles of the Epicurean view of nature by the aid of Democritus’s doctrine of atom-pictures (εἴδωλα). From the surface of bodies—this is the pith of that doctrine—the finest possible particles are constantly being thrown off, which by virtue of their fineness traverse the furthest spaces in an infinitely short time, hurrying through the void. [1229] Many of these exhalations are arrested by some obstacle soon after coming forth, or are otherwise thrown into confusion. In the case of others the atoms for a long time retain the same position and connection which they had in bodies themselves, thus presenting a picture of things, and only lacking corporeal solidity. As these pictures are conveyed to the soul by the various organs of sense, our impressions of things arise. [1230] Even those impressions, which have no corresponding real object, must be referred to such pictures present in the soul. [1231] For often pictures last longer than things themselves; [1232] and often by a casual combination of atoms pictures are formed in the air resembling no one single thing. Sometimes, too, pictures of various kinds are combined on their way to the senses; thus, for instance, the notion of a Centaur is caused by the union of the picture of a man with that of a horse, not only in our imagination, but already previously in the atom-picture. [1233] If, therefore, sensation distorts or imperfectly represents real objects, it must be explained as being due to some change or mutilation in the atom-pictures before they reach our senses. [1234]