Kierkegaard wrote against the grain of his age. The dominant philosophy of his time aimed at grand, all-encompassing rational systems that explained everything from on high. Kierkegaard found this both arrogant and evasive — because it left out the one thing that actually matters to a living person: the concrete, anxious, choosing individual, standing before decisions no system can make for them. Philosophy, he insisted, must speak to that individual, in the first person, about how to exist.
This is the root of his claim that 'truth is subjectivity.' He did not mean that facts are relative or that anything goes. He meant that the truths that matter most for living — about faith, love, and how to spend your one life — cannot be grasped as detached, objective information. They must be inwardly appropriated, held with passion, and enacted. What matters is not just believing the right thing, but the intensity and commitment with which you make it your own. A truth you merely recite is not yet, for you, a truth at all.
The leapFaith, anxiety, and the stages of life.
Nowhere is this clearer than in his treatment of faith. Faith, for Kierkegaard, is not the conclusion of an argument; it is a leap — a wholehearted commitment that goes beyond what reason can secure, made in the face of uncertainty. He explored this most intensely through the biblical Abraham, whose willingness to trust against all comprehension became his image of the 'knight of faith.' He also gave philosophy a searching analysis of anxiety, which he tied to freedom itself: anxiety is the dizziness we feel before the sheer range of what we might choose, the vertigo of possibility.
Kierkegaard mapped human existence into three stages or ways of living: the aesthetic, absorbed in pleasure and immediacy; the ethical, committed to duty and moral seriousness; and the religious, defined by faith and a personal relation to the infinite. Moving between them requires not argument but decisive, transforming choice. Writing often under vivid pseudonyms, he made the drama of individual existence his subject — and by doing so laid the groundwork that later existentialists, from Nietzsche's readers to Sartre and Camus, would build upon.