Question XXVIII of the “Ethics,” complete.

THERE are three regards of union to love. One union is the cause of love: in the love with which one loves oneself this is a substantial union; while in the love with which one loves other beings, it is a union of likeness. Another union is essentially love itself; and this is union of hearts: which is likened to substantial union, inasmuch as the lover is to the object of his love as to himself in the love of friendship; as to something belonging to himself in the love of desire. A third union is the effect of love; and this is a real union which the lover seeks with the object of his love, that they should live together, converse together, and in other relations be conjoined.

  Zeal, whichever way we look at it, comes of intensity of love. For clearly, the greater the intensity wherewith any power tends to an end, the more vigorously does it bear down all opposition or resistance. Since therefore love is a certain movement towards the object loved, intense love seeks to banish all opposition, but in different ways, according as it is the love of desire or of friendship. In the love of desire, he who desires intensely is moved against all that stands in the way of his gaining or quietly enjoying the object of his love; and in this way those who seek pre-eminence are moved against men of seeming eminence as being hindrances to their pre-eminence; and this is the zeal of envy. But the love of friendship seeks the good of the friend: hence, when it is intense, it makes a man bestir himself against all that conflicts with the good of his friend. And in this way we are said to be zealous on behalf of a friend, when if anything is said or done against our friend’s good, we endeavor to repel it. In this way also we are zealous for God, when we endeavor according to our power to repel what goes against the honor and will of God, according to the text, “With zeal have I been zealous for the Lord God of hosts.” And on the text, “The zeal of thy house hath eaten me up,” the gloss (on St. John ii. 17) says: “He is eaten up with a good zeal, who endeavors to correct all the evil that he sees; and if he cannot, tolerates and laments it.”

  Love denotes a certain conformation of the appetitive power to some good. Now nothing is wasted away or injured by simple conformation to an object suited to itself, but rather, if possible, it is perfected and bettered thereby; whereas what is conformed to an object not suited to it is thereby wasted and altered for the worse. The love of a proper good is therefore apt to perfect and better the lover, while the love of a good that is not proper to the lover is apt to waste away the lover and alter him for the worse. Hence a man is perfected and improved most of all by the love of God; and wasted and altered for the worse by the love of sin, according to the text: “They became abominable as those things were which they loved.” This is said of love in respect of its formal element, which is on the part of the appetite. But in respect of the material element, which is some bodily alteration, we do find that love wastes and wears a man away on account of the excess of the alteration: as happens in every act of a spiritual faculty which is exercised by alteration of a bodily organ.

  Every agent acts for some end. But the end is the good desired and loved by each. Hence it is manifest that every agent, whatever it be, does its every action from some love.

  The objection that love is a passion, and that not all things which a man does are done from passion, is valid, touching that love which is a passion existing in the sensitive appetite; but we are speaking now of love in the general sense of the term, including under itself intellectual, rational, animal, and physical love.