On the Morals of the Catholic Church

24. We ought then to love God, the Trinity in unity, Father, Son, and Holy Spirit; for this must be said to be God Himself, for it is said of God, truly and in the most exalted sense, "Of whom are all things, by whom are all things, in whom are all things." Those are Paul’s words. And what does he add? "To Him be glory." All this is exactly true. He does not say, To them; for God is one. And what is meant by, To Him be glory, but to Him be chief and perfect and widespread praise? For as the praise improves and extends, so the love and affection increases in fervor. And when this is the case, mankind cannot but advance with sure and firm step to a life of perfection and bliss. This, I suppose, is all we wish to find when we speak of the chief good of man, to which all must be referred in life and conduct. For the good plainly exists; and we have shown by reasoning, as far as we were able, and by the divine authority which goes beyond our reasoning, that it is nothing else but God Himself. For how can any thing be man’s chief good but that in cleaving to which he is blessed? Now this is nothing but God, to whom we can cleave only by affection, desire, and love.