As the appetitive power, the object loved is said to be in the lover, inasmuch as it is in his affections, by a kind of complacency: causing him either to take pleasure in it, or in its good, when present; or, in the absence of the object loved, by his longing, to tend towards it with the love of concupiscence, or towards the good that he wills to the beloved, with the love of friendship: not indeed from any extrinsic cause (as when we desire one thing on account of another, or wish good to another on account of something else), but because the complacency in the beloved is rooted in the lover's heart. For this reason we speak of love as being "intimate"; and "of the bowels of charity." On the other hand, the lover is in the beloved, by the love of concupiscence and by the love of friendship, but not in the same way. For the love of concupiscence is not satisfied with any external or superficial possession or enjoyment of the beloved; but seeks to possess the beloved perfectly, by penetrating into his heart, as it were. Whereas, in the love of friendship, the lover is in the beloved, inasmuch as he reckons what is good or evil to his friend, as being so to himself; and his friend's will as his own, so that it seems as though he felt the good or suffered the evil in the person of his friend. Hence it is proper to friends "to desire the same things, and to grieve and rejoice at the same," as the Philosopher says (Ethic. ix, 3 and Rhet. ii, 4). 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.
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.
Reply Obj. 1: The beloved is contained in the lover, by being impressed on his heart and thus becoming the object of his complacency. On the other hand, the lover is contained in the beloved, inasmuch as the lover penetrates, so to speak, into the beloved. For nothing hinders a thing from being both container and contents in different ways: just as a genus is contained in its species, and vice versa.
Reply Obj. 2: The apprehension of the reason precedes the movement of love. Consequently, just as the reason divides, so does the movement of love penetrate into the beloved, as was explained above.
Reply Obj. 3: This argument is true of the third kind of mutual indwelling, which is not to be found in every kind of love. ________________________
THIRD ARTICLE [I-II, Q. 28, Art. 3]
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.
Obj. 2: Further, the lover desires the beloved to be united to him. Therefore he draws the beloved to himself, rather than betakes himself into the beloved, going forth out from himself as it were.
Obj. 3: Further, love unites the beloved to the lover, as stated above (A. 1). 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.