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In the realm of philosophy, Bultmann delved into existentialism, a school of thought that emphasized the individual's subjective experiences and personal responsibility in creating meaning in life. Existentialist philosophers, such as Søren Kierkegaard and Martin Heidegger, greatly influenced Bultmann's theological work, particularly his concept of demythologization, which sought to strip away the mythological elements of the Bible to reveal its existential message for modern individuals.