118. For the theory of perception held by Empedokles we have the original words of Theophrastos:—
Empedokles speaks in the same way of all the senses, and says that perception is due to the “effluences” fitting into the passages of each sense. And that is why one cannot judge the objects of another; for the passages of some of them are too wide and those of others too narrow for the sensible object, so that the latter either goes through without touching or cannot enter at all. R. P. 177 b.
He tries, too, to explain the nature of sight. He says that the interior of the eye consists of fire, while round about it is earth and air,[[634]] through which its rarity enables the fire to pass like the light in lanterns (fr. [84]). The passages of the fire and water are arranged alternately; through those of the fire we perceive light objects, through those of the water, dark; each class of objects fits into each class of passages, and the colours are carried to the sight by effluence. R. P. ib.
But eyes are not all composed in the same way; some are composed of like elements and some of opposite; some have the fire in the centre and some on the outside. That is why some animals are keen-sighted by day and others by night. Those which have less fire are keen-sighted in the daytime, for the fire within is brought up to an equality by that without; those which have less of the opposite (i.e. water), by night, for then their deficiency is supplemented. But, in the opposite case, each will behave in the opposite manner. Those eyes in which fire predominates will be dazzled in the daytime, since the fire being still further increased will stop up and occupy the pores of the water. Those in which water predominates will, he says, suffer the same at night, for the fire will be obstructed by the water. And this goes on till the water is separated off by the air, for in each case it is the opposite which is a remedy. The best tempered and the most excellent vision is one composed of both in equal proportions. This is practically what he says about sight.
Hearing, he holds, is produced by sound outside, when the air moved by the voice sounds inside the ear; for the sense of hearing is a sort of bell sounding inside the ear, which he calls a “fleshy sprout.” When the air is set in motion it strikes upon the solid parts and produces a sound.[[635]] Smell, he holds, arises from respiration, and that is why those smell most keenly whose breath has the most violent motion, and why most smell comes from subtle and light bodies.[[636]] As to touch and taste, he does not lay down how nor by means of what they arise, except that he gives us an explanation applicable to all, that sensation is produced by adaptation to the pores. Pleasure is produced by what is like in its elements and their mixture; pain, by what is opposite. R. P. ib.
And he gives a precisely similar account of thought and ignorance. Thought arises from what is like and ignorance from what is unlike, thus implying that thought is the same, or nearly the same, as perception. For after enumerating how we know each thing by means of itself, he adds, “for all things are fashioned and fitted together out of these, and it is by these men think and feel pleasure and pain” (fr. [107]). And for this reason we think chiefly with our blood, for in it of all parts of the body all the elements are most completely mingled. R. P. 178.
All, then, in whom the mixture is equal or nearly so, and in whom the elements are neither at too great intervals nor too small or too large, are the wisest and have the most exact perceptions; and those who come next to them are wise in proportion. Those who are in the opposite condition are the most foolish. Those whose elements are separated by intervals and rare are dull and laborious; those in whom they are closely packed and broken into minute particles are impulsive, they attempt many things and finish few because of the rapidity with which their blood moves. Those who have a well-proportioned mixture in some one part of their bodies will be clever in that respect. That is why some are good orators and some good artificers. The latter have a good mixture in their hands, and the former in their tongues, and so with all other special capacities. R. P. ib.
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. From Aetios[[637]] we learn that 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.[[638]] 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.[[639]]
The theory of vision[[640]] is more complicated; and, as Plato adopted most of it, it is of great importance in the history of philosophy. The eye was conceived, as by Alkmaion ([§ 96]),[[641]] 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. This seems strange to us, because we are accustomed to the idea of images being impressed upon the retina. But looking at a thing no doubt seemed much more like an action proceeding from the eye than a mere passive state.
He was quite 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’) fitting into the pores and perceived.”[[642]] It is not quite clear how these two accounts of vision were reconciled, or how far we are entitled to credit Empedokles with the Platonic theory. The statements which have been quoted seem to imply something very like it.[[643]]