Lev Sestov (1866-1938), who styled himself as an outsider, nevertheless stands at the center of European modernity. Albert Camus admired him. This study examines Sestov's entire body of work in the context of Western philosophy, focusing on his relationship with Nietzsche. Simultaneously a Nietzschean and an apologist for Christianity, Sestov draws on a wide range of sources, from ancient tragedy to contemporary psychiatry, to forge his own path and combat the blind faith in the omnipotence of reason.