Thomas Aquinas

“ If, therefore, the lover goes out from himself, in order to betake himself into the beloved, it follows that the lover always loves the beloved more than himself: which is evidently false. Therefore ecstasy is not an effect of love. ”

“ In yet a third way, mutual indwelling in the love of friendship can be understood in regard to reciprocal love: inasmuch as friends return love for love, and both desire and do good things for one another. ”

“ On the other hand, love of friendship seeks the friend's good: wherefore, when it is intense, it causes a man to be moved against everything that opposes the friend's good. In this respect, a man is said to be zealous on behalf of his friend, when he makes a point of repelling whatever may be said or done against the friend's good. In this way, too, a man is said to be zealous on God's behalf, when he endeavors, to the best of his means, to repel whatever is contrary to the honor or will of God; according to 3 Kings 19:14: "With zeal I have been zealous for the Lord of hosts." ”

“ I answer that, Zeal, whatever way we take it, arises from the intensity of love. For it is evident that the more intensely a power tends to anything, the more vigorously it withstands opposition or resistance. ”

“ Reply to Objection 1: This argument is true of real union. That is necessary to pleasure as being its cause; desire implies the real absence of the beloved: but love remains whether the beloved be absent or present. ”

“ It would seem that love does not cause mutual indwelling, so that the lover be in the beloved and vice versa. For that which is in another is contained in it. But the same cannot be container and contents. Therefore love cannot cause mutual indwelling, so that the lover be in the beloved and vice versa. ”

“ Consequently love of a suitable good perfects and betters the lover; but love of a good which is unsuitable to the lover, wounds and worsens him. Wherefore man is perfected and bettered chiefly by the love of God: but is wounded and worsened by the love of sin, according to Osee 9:10: "They became abominable, as those things which they loved." ”

“ Consequently in so far as he reckons what affects his friend as affecting himself, the lover seems to be in the beloved, as though he were become one with him: but in so far as, on the other hand, he wills and acts for his friend's sake as for his own sake, looking on his friend as identified with himself, thus the beloved is in the lover. ”

“ This argument is true of the third kind of mutual indwelling, which is not to be found in every kind of love.
Whether ecstasy is an effect of love?
Objection 1: It would seem that ecstasy is not an effect of love. For ecstasy seems to imply loss of reason. But love does not always result in loss of reason: for lovers are masters of themselves at times. Therefore love does not cause ecstasy. ”

“ But in respect of the material element in the passion of love, i.e. a certain bodily change, it happens that love is hurtful, by reason of this change being excessive: just as it happens in the senses, and in every act of a power of the soul that is exercised through the change of some bodily organ. ”