There are 3 types of sadness. Grief (mourning). Melancholy. Depression (in the non-clinical sense). Each signifying a relationship to the loss of an object.
Grief is sadness over the loss of an object that I once had. It is when something is taken away from me. When someone dies. When some situation changes. It is not so bad a deal. It is merely a part of the human condition, to grieve, and to accept that fact which causes you to grieve. You get over it by accepting reality in its brutality. (The danger here is, of course, to dwell in grief, and even escape back to the previous world, like the protagonist of Psycho—to pretend that nothing has ever happened. To be fixated in a single fantasy.) Grief is still rather naive.
There, then, is melancholy. Melancholy is when you are sad for the future loss of the objects that you currently have, when you realize how transient everything is, that love, friendship, life, are all brief cracks of light between two eternities of darkness. It is the light sense of doom that envelopes oneself late at night—when death terrifies me. But melancholy is not necessarily negative. For this realization can either throw you into depression, or urge you into a Sisyphean love for the world. As Keats wrote in Ode on Melancholy,
She [Mistress Melancholy] dwells with Beauty—Beauty that must die;
And Joy, whose hand is ever at his lips
Bidding adieu; and aching Pleasure nigh,
Turning to poison while the bee-mouth sips:
Ay, in the very temple of Delight
Veil’d Melancholy has her sovran shrine,
Though seen of none save him whose strenuous tongue
Can burst Joy’s grape against his palate fine;
His soul shalt taste the sadness of her might,
And be among her cloudy trophies hung.
Melancholy is about the beauty that must die, of the joy that always bids adieu, the pleasure that turns to poison. But only one who really has lived can be taken into melancholy, to be among her “cloudy trophies hung.”
At last there is depression. To follow the previous schemes, depression is when you are sad for the future loss of an object that you have not yet possessed. It is the premonition of the futility of everything, even things that you desire. (Hence I read yesterday that people who are depressed find no motivation to even eat…) It inverts your desire into despair, shaking you out of the cycle of desire not be eliminating them, but by constantly reminding you, whenever you desire, that the object of desire is never as you imagine it to be, that the object of desire is phantasmic. Therefore there is no point of desiring, no point of obtaining anything (though one deeply wishes to do so). Depression is not the simple negation of desire—a no desire. But an indefinite judgement, a negation that incorporates desire in its own scheme, a non-desire, a latent possibility in all desire, that its lack protrudes more so than its being.
What then goes wrong in depression? Not the diagnostic, perhaps, for it is perfectly true that what we obtain through desire would be lost sooner or later. But one’s reaction towards it. There may be a heroic stance (and it is heroic because it is almost an impossibility in its difficulty) of affirming the transience, the appearing, the evanescent. For if one takes them sufficiently seriously, a single moment can be experienced as onto-existentially necessary, as if the entire universe was created for this second. This is why double-negation is the ultimate ethical stance. To negate the negation of life.