For Kierkegaard, in order to apprehend the absolute, the mind must radically empty itself of objective content. What supports this radical emptying, however, is the desire for the absolute. Kierkegaard names this desire Passion.
According to Kierkegaard, the human self desires that which is beyond reason. Desire itself appears to be a desire for the infinite, as Plato once wrote. Even the desire to propagate, according to Plato, is a kind of desire for immortality—that is, we wish to live on in time through our children and their children. Erotic love itself appears as an example of this desire for something beyond the purely finite. It is a taste of what could be, if only it could continue beyond the boundaries of time and space. As the analogy implies, humans seek something beyond the here and now. The question remains, however, why is it that human pathos or passion is the most precious thing? In some ways, it might have to do with our status as existential beings. It is not thought that gets us through life—it is action; and what motivates and sustains action is passion, the desire to overcome hardships, pain, and suffering. It is also passion that enables us to die for ideals in the name of a higher reality. While a scientist might see this as plain emotion or simple animal desire, Kierkegaard sees it as that which binds to the source of life itself. The desire to live, and to live in the right way, for the right reasons, and with the right desires, is a holy and sacred force. For Kierkegaard all Christian action should have its ground in love, which is a passion.
If anyone is unwilling to learn from Christianity to love himself in the right way, he cannot love the neighbor either. He can perhaps hold together with another or a few other persons, “through thick and thin,” as it is called, but this is by no means loving the neighbor. To love yourself in the right way and to love the neighbor correspond perfectly to one another, fundamentally they are one and the same thing. When the Law’s as yourself has wrested from you the self-love that Christianity sadly enough must presuppose to be in every human being, then you actually have learned to love yourself. The Law is therefore: you shall love yourself in the same way as you love your neighbor when you love him as yourself. Whoever has any knowledge of people will certainly admit that just as he has often wished to be able to move them to relinquish self-love, he has also had to wish that it were possible to teach them to love themselves. When the bustler wastes his time and powers in the service of the futile, inconsequential pursuits, is that not because he has not learned rightly to love himself? When the light-minded person throws himself almost like a nonentity into the folly of the moment and makes nothing of it, is this not because he does not know how to love himself rightly? When the depressed person desires to be rid of life, indeed of himself, is this not because he is unwilling to learn earnestly and rigorously to love himself? When someone surrenders to despair because the world or another person has faithlessly left him betrayed, what then is his fault (his innocent suffering is not referred to here) except not loving himself in the right way? When someone self-tormentingly thinks to do God a service by torturing himself, what is his sin except not willing to love himself in the right way? And if, alas, a person presumptuously lays violent hands upon himself, is not his sin precisely this, that he does not rightly love himself in the sense in which a person ought to love himself? Oh, there is a lot of talk in the world about treachery, and faithlessness, and, God help us, it is unfortunately all too true, but still let us never because of this forget that the most dangerous traitor of all is the one every person has within himself. This treachery whether it consists in selfishly loving oneself or consists in selfishly not willing to love oneself in the right way – this treachery is admittedly a secret. No cry is raised as it usually is in the case of treachery and faithlessness. But is it not therefore all the more important that Christianity’s doctrine should be brought to mind again and again, that a person shall love his neighbor as himself, that is as he ought to love himself? … You shall love – this, then is the word of the royal Law. Works of Love, p. 22-24
One can also look at this from the perspective of what the meaning of our existence is. Why suffer what humans have suffered, the pain and despair—what meaning can all of this have? For Kierkegaard, there is no meaning unless passion, the emotions and will of humans, has a divine source.
Passion is closely aligned with faith in Kierkegaard's thought. Faith as a passion is what drives humans to seek reality and truth in a transcendent world, even though everything we can know intellectually speaks against it. To live and die for a belief, to stake everything one has and is in the belief in something that has a higher meaning than anything in the world—this is belief and passion at their highest.
Kierkegaard wrote of the subjective thinker's task in his Concluding Unscientific Postscript . Intellectual reason had been deified by Hegel in his theology and Kierkegaard felt this would lead to the objectification of religion.
There is an old proverb: oratio, tentatio, meditatio, faciunt theologum [prayer, trial, meditation, make a theologian]. Similarly, for a subjective thinker, imagination, feeling and dialectics in impassioned existence-inwardness are required. But first and last, passion, because for an existing person it is impossible to think about existence without becoming passionate, inasmuch as existing is a prodigious contradiction from which the subjective thinker is not to abstract, for then it is easy, but in which he is to remain. In a world-historical dialectic, individuals fade away into humankind; in a dialectic such as that it is impossible to discover you and me, an individual existing human being, even if new magnifying glasses for the concrete are invented. The subjective thinker is a dialectician oriented to the existential; he has the intellectual passion to hold firm the qualitative disjunction. But, on the other hand, if the qualitative disjunction is used flatly and simply, if it is applied altogether abstractly to the individual human being, then one can run the ludicrous risk of saying something infinitely decisive, and of being right in what one says, and still not say the least thing. Therefore, in the psychological sense it is really remarkable to see the absolute disjunction deceitfully used simply for evasion. When the death penalty is placed on every crime, the result is that no crimes at all are punished. It is the same with the absolute disjunction when applied flatly and simply; it is just like a silent letter-it cannot be pronounced or, if it can be pronounced, it says nothing. The subjective thinker, therefore, has with intellectual passion the absolute disjunction as belonging to existence, but he has it as the final decision that prevents everything from ending in a quantifying. Thus he has it readily available, but not in such a way that by abstractly recurring to it, he just frustrates existence. The subjective thinker, therefore, has also esthetic passion and ethical passion, whereby concretion is gained. All existence-issues are passionate, because existence, if one becomes conscious of it, involves passion. To think about them so as to leave out passion is not to think about them at all, is to forget the point that one indeed is oneself and existing person. Yet the subjective thinker is not a poet even if he is also a poet, not an ethicist even if he is also an ethicist, but is also a dialectician and is himself essentially existing, whereas the poet’s existence is inessential in relation to the poem, and likewise the ethicist’s in relation to the teaching, and the dialectician’s in relation to the thought. The subjective thinker is not a scientist-scholar; he is an artist. To exist is an art. The subjective thinker is esthetic enough for his life to have esthetic content, ethical enough to regulate it, dialectical enough in thinking to master it. The subjective thinker’s task is to understand himself in existence. p. 350-351