ain,
according as it is affected in some sensible qualities, as in the
movement of alteration; and thus to sense movement and rest is, in a
way, to sense one thing and many. Now quantity is the proximate
subject of the qualities that cause alteration, as surface is of
color. Therefore the common sensibles do not move the senses first
and of their own nature, but by reason of the sensible quality; as
the surface by reason of color. Yet they are not accidental
sensibles, for they produce a certain variety in the immutation of
the senses. For sense is immuted differently by a large and by a
small surface: since whiteness itself is said to be great or small,
and therefore it is divided according to its proper subject.

Reply Obj. 3: As the Philosopher seems to say (De Anima ii, 11),
the sense of touch is generically one, but is divided into several
specific senses, and for this reason it extends to various
contrarieties; which senses, however, are not separate from one
another in their organ, but are spread throughout the whole body, so
that their distinction is not evident. But taste, which perceives the
sweet and the bitter, accompanies touch in the tongue, but not in the
whole body; so it is easily distinguished from touch. We might also
say that all those contrarieties agree, each in some proximate genus,
and all in a common genus, which is the common and formal object of
touch. Such common genus is, however, unnamed, just as the proximate
genus of hot and cold is unnamed.

Reply Obj. 4: The sense of taste, according to a saying of the
Philosopher (De Anima ii, 9), is a kind of touch existing in the
tongue only. It is not distinct from touch in general, but only from
the species of touch distributed in the body. But if touch is one
sense only, on account of the common formality of its object: we must
say that taste is distinguished from touch by reason of a different
formality of immutation. For touch involves a natural, and not only a
spiritual, immutation in its organ, by reason of the quality which is
its proper object. But the organ of taste is not necessarily immuted
by a natural immutation by reason of the quality which is its proper
object, so that the tongue itself becomes sweet and bitter: but by
reason of a quality which is a preamble to, and on which is based,
the flavor, which quality is moisture, the object of touch.
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FOURTH ARTICLE [I, Q. 78, Art. 4]

Whether the Interior Sens