I answer that, As stated above (A. 1), pleasure arises from union with a suitable object perceived or known.  Now, in the operations of the soul, especially of the sensitive and intellectual soul, it must be noted that, since they do not pass into outward matter, they are acts or perfections of the agent, e.g. to understand, to feel, to will and the like:  because actions which pass into outward matter, are actions and perfections rather of the matter transformed; for “movement is the act produced by the mover in the thing moved” (Phys. iii, 3).  Accordingly the aforesaid actions of the sensitive and intellectual soul, are themselves a certain good of the agent, and are known by sense and intellect.  Wherefore from them also does pleasure arise, and not only from their objects.

If therefore we compare intellectual pleasures with sensible pleasures, according as we delight in the very actions, for instance in sensitive and in intellectual knowledge; without doubt intellectual pleasures are much greater than sensible pleasures.  For man takes much more delight in knowing something, by understanding it, than in knowing something by perceiving it with his sense.  Because intellectual knowledge is more perfect; and because it is better known, since the intellect reflects on its own act more than sense does.  Moreover intellectual knowledge is more beloved:  for there is no one who would not forfeit his bodily sight rather than his intellectual vision, as beasts or fools are deprived thereof, as Augustine says in De Civ.  Dei (De Trin. xiv, 14).

If, however, intellectual spiritual pleasures be compared with sensible bodily pleasures, then, in themselves and absolutely speaking, spiritual pleasures are greater.  And this appears from the consideration of the three things needed for pleasure, viz. the good which is brought into conjunction, that to which it is conjoined, and the conjunction itself.  For spiritual good is both greater and more beloved than bodily good:  a sign whereof is that men abstain from even the greatest bodily pleasures, rather than suffer loss of honor which is an intellectual good.  Likewise the intellectual faculty is much more noble and more knowing than the sensitive faculty.  Also the conjunction is more intimate, more perfect and more firm.  More intimate, because the senses stop at the outward accidents of a thing, whereas the intellect penetrates to the essence; for the object of the intellect is “what a thing is.”  More perfect, because the conjunction of the sensible to the sense implies movement, which is an imperfect act:  wherefore sensible pleasures are not perceived all at once, but some part of them is passing away, while some other part is looked forward to as yet to be realized, as is manifest in pleasures of the table and in sexual pleasures:  whereas intelligible things are without movement:  hence pleasures of this kind are realized all at once.  More firm; because the objects of bodily pleasure are corruptible, and soon pass away; whereas spiritual goods are incorruptible.