In Religion within the Boundaries of Mere Reason Kant refers frequently to the biblical symbol of the «heart». My paper offers a comprehensive survey of Kant’s use of this symbol and explains its several meaning. The research aims at better understanding of three well-known topics: 1. the analysis of the heart as a symbol explains how the propensity to evil could be a subjective ground for action; 2. the perversity of the heart is a key concept that justifies Kant’s proof of the wickedness of human nature; 3. the rebirth of the heart is the only way to outweigh evil and is the indispensable premise for obtaining God’s grace.

Keywords: Kant; Philosophy of Religion; Ethics.