"There are some things, then, which are to be enjoyed, others which are to be used, others still which enjoy and use. Those things which are objects of enjoyment make us happy. Those things which are objects of use assist, and (so to speak) support us in our efforts after happiness, so that we can attain the things that make us happy and rest in them. We ourselves, again, who enjoy and use these things, being placed among both kinds of objects, if we set ourselves to enjoy those which we ought to use, are hindered in our course, and sometimes even led away from it; so that, getting entangled in the love of lower gratifications, we lag behind in, or even altogether turn back from, the pursuit of the real and proper objects of enjoyment." (On Christian Doctrine, 1, 3)
“Following after God is the desire of happiness; to reach God is happiness itself.” (De Moribus Ecclesiae Catholicae, 11, 18)
“Some (angels and men alike) steadily set up their rest in the good that is common to them all, in God Himself, His eternity, truth, love. Others (angels and men) choose rather to delight in their own power, as though they were their own sufficient good, and so have drifted from the higher general good and source of happiness to purposes of their own…. If it is asked why the one are happy, the right answer is, Because they cleave to God. If it is asked why the others are miserable, the right answer is, Because they do not cleave to God. There is no good capable of making any rational or intellectual creature happy except God.” (The City of God, 12, 1)
St. Augustine in His Cell, by Sandro Botticelli. Tempera on panel, 1490-94; Galleria degli Uffizi, Florence.