Lev Isaakovich Shestov, born Yeguda Leib Shvartsman, was a Russian existentialist and religious philosopher. He is best known for his critiques of both philosophic rationalism and positivism. His work advocated a movement beyond reason and metaphysics, arguing that these are incapable of conclusively establishing truth about ultimate problems, including the nature of God or existence. Contemporary scholars have associated his work with the label "anti-philosophy."