Page:Early Greek philosophy by John Burnet, 3rd edition, 1920.djvu/262

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Perception, then, is due to the meeting of an element in us with the same element outside. This takes place when the pores of the organ of sense are neither too large nor too small for the "effluences" which all things are constantly giving off (fr. 89). Smell was explained by respiration. The breath drew in along with it the small particles which fit into the pores. Empedokles proved this by the example of people with a cold in their head, who cannot smell, just because they have a difficulty in breathing. We also see from fr. 101 that the scent of dogs was referred to in support of the theory. Empedokles seems to have given no detailed account of smell, and did not refer to touch at all. Hearing was explained by the motion of the air which struck upon the cartilage inside the ear and made it swing and sound like a bell.

The theory of vision is more complicated; and, as Plato makes his Timaios adopt most of it, it is of great importance in the history of philosophy. The eye was conceived, as by Alkmaion (§ 96), to be composed of fire and water. Just as in a lantern the flame is protected from the wind by horn (fr. 84); so the fire in the iris is protected from the water which surrounds it in the pupil by membranes with very fine pores, so that, while the fire can pass out, the water cannot get in. Sight is produced by the fire inside the eye going forth to meet the object.

Empedokles was aware, too, that "effluences," as he called them, came from things to the eyes as well; for he defined colours as "effluences from forms (or 'things')