Abstract This study examines the spiritual radicalism of Abraham Joshua Heschel through analysis of his theological writings, social activism, and prophetic consciousness. Using textual analysis of Heschel's major works and biographical examination of his public engagement, this research demonstrates how Heschel's "Depth Theology" challenged conventional religious institutions while advocating for authentic spiritual encounter. The methodology combines literary analysis of Heschel's poetic prose style with theological interpretation of his concept of three-dimensional religious experience encompassing self, community, and divine presence. Key findings reveal that Heschel's radicalism emerged from his integration of prophetic tradition with contemporary social action, exemplified through his civil rights activism, opposition to the Vietnam War, and interfaith dialogue efforts. His approach to prayer as "subversive" activity demonstrates the inseparable connection between spiritual authenticity and moral responsibility. The study concludes that Heschel's spiritual radicalism represents a creative synthesis of traditional Jewish mysticism and modern existential concerns, offering a model for religious engagement that transcends institutional complacency. His prophetic sensitivity manifested in both scholarly works on biblical prophecy and direct political action, illustrating how genuine religious experience necessitates confrontation with social injustice. This analysis contributes to understanding twentieth-century Jewish theology and the relationship between mystical experience and social activism in modern religious thought.