31.5

I answer that, As stated above (Article 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.