 Having established the physical basis of the world, Epicurus proceeds to explain the nature of the soul (this, at least, is the order in which Lucretius sets things out). This too, of course, consists of atoms: first, there is nothing that is not made up of atoms and void (secondary qualities are simply accidents of the arrangement of atoms), and second, an incorporeal entity could neither act on nor be moved by bodies, as the soul is seen to do (e.g., it is conscious of what happens to the body, and it initiates physical movement). Epicurus maintains that soul atoms are particularly fine and are distributed throughout the body (LH 64), and it is by means of them that we have sensations (aisthêseis) and the experience of pain and pleasure, which Epicurus calls pathê (a term used by Aristotle and others to signify emotions instead). Body without soul atoms is unconscious and inert, and when the atoms of the body are disarranged so that it can no longer support conscious life, the soul atoms are scattered and no longer retain the capacity for sensation (LH 65). There is also a part of the human soul that is concentrated in the chest, and is the seat of the higher intellectual functions. The distinction is important, because it is in the rational part that error of judgment enters in. Sensation, like pain and pleasure, is incorrigible just because it is a function of the non-rational part, which does not modify a perception — that is, the reception of lamina emitted from macroscopic bodies — by the addition of opinion or belief.