Søren Kierkegaard (1813–1855) was a Danish philosopher, theologian, and cultural critic who is widely considered the father of existentialism. Writing in Copenhagen during a period of Hegelian dominance, he launched a passionate critique of systematic philosophy's attempt to explain all of existence through abstract reason. Against Hegel's grand synthesis, Kierkegaard insisted on the irreducible importance of the individual, subjective experience, personal choice, and passionate commitment. His concept of the "leap of faith" described the moment when an individual must make a fundamental commitment that cannot be justified by rational argument alone. He outlined three "stages on life's way": the aesthetic (pleasure and immediacy), the ethical (duty and moral responsibility), and the religious (personal relationship with God through faith). His exploration of anxiety, despair, and the anguish of freedom anticipated themes later developed by Heidegger, Sartre, and Camus. Kierkegaard wrote under numerous pseudonyms, each representing a different philosophical perspective. His works include Either/Or, Fear and Trembling, The Concept of Anxiety, and The Sickness Unto Death.