On Sense And The Sensible
figure, magnitude, motion, number: while hearing announces only the
distinctive qualities of sound, and, to some few animals, those also
of voice. indirectly, however, it is hearing that contributes most
to the growth of intelligence. For rational discourse is a cause of
instruction in virtue of its being audible, which it is, not directly,
but indirectly; since it is composed of words, and each word is a
thought-symbol. Accordingly, of persons destitute from birth of either
sense, the blind are more intelligent than the deaf and dumb.
Of the distinctive potency of each of the faculties of sense
enough has been said already.
But as to the nature of the sensory organs, or parts of the body
in which each of the senses is naturally implanted, inquirers now
usually take as their guide the fundamental elements of bodies. Not,
however, finding it easy to coordinate five senses with four elements,
they are at a loss respecting the fifth sense. But they hold the organ
of sight to consist of fire, being prompted to this view by a
certain sensory affection of whose true cause they are ignorant.
This is that, when the eye is pressed or moved, fire appears to
flash from it. This naturally takes place in darkness, or when the
eyelids are closed, for then, too, darkness is produced.
This theory, however, solves one question only to raise another;
for, unless on the hypothesis that a person who is in his full
senses can see an object of vision without being aware of it, the
eye must on this theory see itself. But then why does the above
affection not occur also when the eye is at rest? The true explanation
of this affection, which will contain the answer to our question,
and account for the current notion that the eye consists of fire, must
be determined in the following way: Things which are smooth have the
natural property of shining in darkness, without, however, producing
light. Now, the part of the eye called 'the black', i.e. its central