Goodness, armed with power, is corrupted; and pure love without power is destroyed.

Niebuhr is pointing to a tragic tension at the heart of moral and political life. When “goodness” gains coercive power, it is tempted to justify harsh means, self-righteousness, or domination in the name of virtue—thereby becoming corrupted. Yet “pure love” that refuses power altogether can be crushed by injustice, because it lacks the capacity to protect itself or others. The line encapsulates Niebuhr’s Christian realism: ethics must reckon with sin, egoism, and structural injustice, so responsible action often requires power tempered by humility, accountability, and repentance rather than either naïve idealism or cynical force.