Nature of love

Plotinus extends the erōs of Plato's Symposium: love is that drive born of lack which carries the soul from sensible beauty toward intelligible Beauty, and thence toward the One, source of all beauty. It is an ascending love, a desire to be united with that from which one proceeds. A note of gift nonetheless surfaces, for the One itself lacks nothing and overflows by pure superabundance, which reverses the lack at the summit.

Enneads, III, 5 (On Love) · Enneads, VI, 7, 31-34

Platonic eros is desire born of lack: child of Poros and Penia, it seeks to possess what it wants, the beautiful and the good. From the beauty of bodies the lover ascends by degrees to the Form of the Beautiful, along the ladder of the Symposium.

Plato, Symposium, 201d-212c, speech of Diotima · Plato, Phaedrus, 244a-257b

Romantic love is wholly aspiration and lack: in the beloved it desires the infinite itself, and it is from this never-filled distance that it draws its intensity. Far from tranquil possession, it is a surge toward a glimpsed absolute, the longing for a union that slips away, which is why it borders so readily on night and on the unreachable.

Novalis, Hymns to the Night · Hölderlin, Hyperion

In The Passions of the Soul, love is a passion, an emotion of the soul caused by the body's spirits, that inclines the will to join itself to objects which appear suitable to it. Descartes distinguishes two loves: the love of concupiscence, which desires for oneself what one lacks, and the love of benevolence, which wills the good of the beloved. To the passion undergone is added generosity, the firm disposition to make good use of one's free will, to esteem others and to unite with them, which governs and ennobles love instead of merely suffering it.

The Passions of the Soul, arts. 79-83 (love); arts. 153-156 (generosity)

The supreme love is for Thomas charity (caritas), the Latin rendering of agape: a love of benevolence that wills the other's good and descends from God toward the creature rather than rising from lack toward the good, as Platonic eros does. But Thomas gives it a precise and decisive definition: charity is a friendship (amicitia) of the human being with God, Aristotle's very category taken up and transposed: founded on the sharing of beatitude, it supposes, like every friendship, mutual benevolence and a communion. The gift remains primary, since it is God who loves first and makes this friendship possible by grace, yet it takes the reciprocal form of philia, not that of a one-way gift; the old upward thrust of desire toward the good nonetheless persists as a residual share.

Summa Theologiae, IIa-IIae, q. 23 (charity as friendship)

Beauvoir criticizes the love in which woman alienates herself and makes herself the other's object: the woman in love who loses herself in the beloved, for want of a project of her own, is a figure of bad faith. To this love-as-lack that seeks to complete itself in another, she opposes authentic love, the reciprocal bond of two freedoms that recognize and choose one another without either dissolving into the other. It is an existential philia, made of mutual recognition, in which the share of gift lies in each willing the other's freedom as their own.

The Second Sex (1949), vol. II, "The Woman in Love"

At the heart of love Spinoza sees neither lack nor gift but a joy: to love is to pass to a greater perfection, a joy referred to the idea of its cause (Ethics, III). Love is therefore not the surge of a void toward what would fill it, but the striving (conatus) of power toward what increases it, which keeps a kinship with eros without its pathos of lack. Among human beings this striving culminates in the friendship of those guided by reason, who agree in nature, are mutually useful and want nothing for themselves that they do not also want for others: a rational philia, reciprocal and chosen. At the summit, the intellectual love of God exceeds every interpersonal bond: a love without return, in which the sage does not require to be loved back, closer to disinterested gift than to possession.

Ethics, III (definition of love); IV, props. 35-37 and 70-71 (the friendship of reasonable people); V, props. 19 and 32-37 (the intellectual love of God)