108. This implies the degradation of the ‘primary qualities of body’ from the position which they hold in the Second Book of the Essay, as the real, _par excellence_, to that of a nominal essence. In the Second Book, just as the complex of ideas, received and to be received from a substance, is taken for the real thing without disturbance from the antithesis between reality and ‘ideas in the mind,’ so the primary qualities of body are taken not only as real, but as the sources of all other reality. Body, the real thing, copying itself upon the mind in an idea of sensation (that of solidity), carries with it from reality into the mind those qualities which ‘the mind finds inseparable from it,’ with all their modes. ‘A piece of manna of a sensible bulk is able to produce in us the idea of a round or square figure, and, by being removed from one place to another, the idea of motion. This idea of motion represents it, as it really is in the manna, moving; a circle or square are the same, whether in idea or existence, in the mind or in the manna; and this both motion and figure are really in the manna, whether we take notice of them or no.’ (Book II. chap. viii. sec. 18.) To the unsophisticated man, taking for granted that the ‘sensible bulk’ of the manna is a ‘real essence,’ this statement will raise no difficulties. But when he has learnt from Locke himself that the ‘sensible bulk,’ so far as we can think and speak of it, must consist in the ideas which it is said to produce, the question as to the real existence of these must arise. It turns out that they ‘really exist,’ so far as they represent the impact of a body copying itself in actually present sensation, and that from their reality, accordingly, must be excluded all qualities that accrue to the present sensation from its relation to the past. Can the ‘primary qualities’ escape this exclusion? Are the ‘primary qualities’ then, a ‘nominal essence’?