This difference followed naturally from the opinions of the two philosophers on the nature of the soul or mind. Anaxagoras supposed it peculiar in itself, and dissimilar to the Homoeomeries without. Empedokles conceived it as a compound of the four elements, analogous to all that was without: hence man knew each exterior element by its like within himself--earth by earth, water by water, &c.] [Footnote 179: Anaxag. Fr. 19, Schaub.; Sextus Empiric. adv. Mathem. vii. 91-140; Cicero, Academ. i. 12. Anaxagoras remarked that the contrast between black and white might be made imperceptible to sense by a succession of numerous intermediate colours very finely graduated. He is said to have affirmed that snow was really black, notwithstanding that it appeared white to our senses: since water was black, and snow was only frozen water (Cicero, Academ. iv. 31; Sext. Empir. Pyrrhon. Hypotyp. i. 33). "Anaxagoras non modo id ita esse (_sc._ albam nivem esse) negabat, sed sibi, quia sciret aquam nigram esse, unde illa concreta esset, albam ipsam esse _ne videri quidem_." Whether Anaxagoras ever affirmed that snow did not _appear to him_ white, may reasonably be doubted: his real affirmation probably was, that snow, though it appeared white, was not really white. And this affirmation depended upon the line which he drew between the fact of sense, the phenomenal, the relative, on one side--and the substratum, the real, the absolute, on the other. Most philosophers recognise a distinction between the two; but the line between the two has been drawn in very different directions. Anaxagoras assumed as his substratum, real, or absolute, the Homoeomeries--numerous primordial varieties of matter, each with its inherent qualities. Among these varieties he reckoned _water_, but he did not reckon _snow_. He also considered that water was really and absolutely black or dark (the Homeric [Greek: me/lan u(/dôr])--that blackness was among its primary qualities. Water, when consolidated into snow, was so disguised as to produce upon the spectator the appearance of whiteness; but it did not really lose, nor could it lose, its inherent colour. A negro covered with white paint, and therefore looking white, is still really black: a wheel painted with the seven prismatic colours, and made to revolve rapidly, will look white, but it is still really septi-coloured: _i.e._ the state of rapid revolution would be considered as an exceptional state, not natural to it. Compare Plato, Lysis, c. 32, p. 217 D.] [Side-note: The doctrines of Anaxagoras were regarded as offensive and impious.]