I answer that, As stated above (Q. 25, A. 2, ad 1; Q. 27, A. 4, ad 1), everything gives pleasure according as it is loved.  Now, as stated in Metaph. i, 1, the senses are loved for two reasons:  for the purpose of knowledge, and on account of their usefulness.  Wherefore the senses afford pleasure in both these ways.  But because it is proper to man to apprehend knowledge itself as something good, it follows that the former pleasures of the senses, i.e. those which arise from knowledge, are proper to man:  whereas pleasures of the senses, as loved for their usefulness, are common to all animals.

If therefore we speak of that sensible pleasure which is by reason of knowledge, it is evident that the sight affords greater pleasure than any other sense.  On the other hand, if we speak of that sensible pleasure which is by reason of usefulness, then the greatest pleasure is afforded by the touch.  For the usefulness of sensible things is gauged by their relation to the preservation of the animal’s nature.  Now the sensible objects of touch bear the closest relation to this usefulness:  for the touch takes cognizance of those things which are vital to an animal, namely, of things hot and cold and the like.  Wherefore in this respect, the pleasures of touch are greater as being more closely related to the end.  For this reason, too, other animals which do not experience sensible pleasure save by reason of usefulness, derive no pleasure from the other senses except as subordinated to the sensible objects of the touch:  “for dogs do not take delight in the smell of hares, but in eating them; . . . nor does the lion feel pleasure in the lowing of an ox, but in devouring it” (Ethic. iii, 10).

Since then the pleasure afforded by touch is the greatest in respect of usefulness, and the pleasure afforded by sight the greatest in respect of knowledge; if anyone wish to compare these two, he will find that the pleasure of touch is, absolutely speaking, greater than the pleasure of sight, so far as the latter remains within the limits of sensible pleasure.  Because it is evident that in everything, that which is natural is most powerful:  and it is to these pleasures of the touch that the natural concupiscences, such as those of food, sexual union, and the like, are ordained.  If, however, we consider the pleasures of sight, inasmuch sight is the handmaid of the mind, then the pleasures of sight are greater, forasmuch as intellectual pleasures are greater than sensible.

Reply Obj. 1:  Joy, as stated above (A. 3), denotes pleasure of the soul; and this belongs principally to the sight.  But natural pleasure belongs principally to the touch.

Reply Obj. 2:  The sight is loved most, “on account of knowledge, because it helps us to distinguish many things,” as is stated in the same passage (Metaph. i, 1).

Reply Obj. 3:  Pleasure causes carnal love in one way; the sight, in another.  For pleasure, especially that which is afforded by the touch, is the final cause of the friendship which is for the sake of the pleasant:  whereas the sight is a cause like that from which a movement has its beginning, inasmuch as the beholder on seeing the lovable object receives an impression of its image, which entices him to love it and to seek its delight. ________________________