“Wherefore men take pleasure in their children, and in their own works, as being things on which they bestow a share of their own good. Another principle is man's habitual inclination to do good, by reason of which doing good becomes connatural to him: for which reason the liberal man takes pleasure in giving to others. The third principle is the motive: for instance when a man is moved by one whom he loves, to do good to someone: for whatever we do or suffer for a friend is pleasant, because love is the principal cause of pleasure.
Reply Obj. 1: Spending gives pleasure as showing forth one's good. But in so far as it empties us of our own good it may be a cause of sadness; for instance when it is excessive.
Reply Obj. 2: Prodigality is an excessive spending, which is unnatural: wherefore prodigality is said to be contrary to nature.”