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. _______________________
FOURTH ARTICLE [I, Q. 78, Art. 4]
Whether the Interior Senses Are Suitably Distinguished?
Objection 1: It would seem that the interior senses are not suitably distinguished. For the common is not divided against the proper. Therefore the common sense should not be numbered among the interior sensitive powers, in addition to the proper exterior senses.
Obj. 2: Further, there is no need to assign an interior power of apprehension when the proper and exterior sense suffices. But the proper and exterior senses suffice for us to judge of sensible things; for each sense judges of its proper object. In like manner they seem to suffice for the perception of their own actions; for since the action of the sense is, in a way, between the power and its object, it seems that sight must be much more able to perceive its own vision, as being nearer to it, than the color; and in like manner with the other senses. Therefore for this there is no need to assign an interior power, called the common sense.
Obj. 3: Further, according to the Philosopher (De Memor. et Remin. i), the imagination and the memory are passions of the "first sensitive." But passion is not divided against its subject. Therefore memory and imagination should not be assigned as powers distinct from the senses.
Obj. 4: Further, the intellect depends on the senses less than any power of the sensitive part. But the intellect knows nothing but what it receives from the senses; whence we read (Poster. i, 8), that "those who lack one sense lack one kind of knowledge." Therefore much less should we assign to the sensitive part a power, which they call the "estimative" power, for the perception of intentions which the sense does not perceive.
Obj. 5: Further, the action of the cogitative power, which consists in comparing, adding and dividing, and the action of the reminiscence, which consists in the use of a kind of syllogism for the sake of inquiry, is not less distant from the actions of the estimative and memorative powers, than the action of the estimative is from the action of the imagination. Therefore either we must add the cognitive and reminiscitive to the estimative and memorative powers, or the estimative and memorative powers should not be made distinct from the imagination.
Obj. 6: Further, Augustine (Gen. ad lit. xii, 6, 7, 24) describes three kinds of vision; namely, corporeal, which is the action of the sense; spiritual, which is an action of the imagination or phantasy; and intellectual, which is an action of the intellect. Therefore there is no interior power between the sense and intellect, besides the imagination.
On the contrary, Avicenna (De Anima iv, 1) assigns five interior sensitive powers; namely, "common sense, phantasy, imagination, and the estimative and memorative powers."