Pain itself can be pleasurable accidentally in so far as it is accompanied by wonder, as in stage-plays; or in so far as it recalls a beloved object to one's memory, and makes one feel one's love for the thing, whose absence gives us pain. Consequently, since love is pleasant, both pain and whatever else results from love, in so far as they remind us of our love, are pleasant.
Thomas AquinasIt is requisite for the relaxation of the mind that we make use, from time to time, of playful deeds and jokes.
Thomas AquinasEvery judgement of conscience, be it right or wrong, be it about things evil in themselves or morally indifferent, is obligatory, in such wise that he who acts against his conscience always sins.
Thomas AquinasIt would seem that the ingratitude, whereby a subsequent sin causes the return of sins previously forgiven, is a special sin. For, the giving of thanks belongs to counter passion, which is a necessary condition of justice. But justice is a special virtue. Therefore this ingratitude is a special sin. Thanksgiving is a special virtue. But ingratitude is opposed to thanksgiving. Therefore ingratitude is a special sin.
Thomas Aquinas