Darkness cannot drive out darkness; only light can do that. Hate cannot drive out hate; only love can do that. Hate multiplies hate, violence multiplies violence, and toughness multiplies toughness in a descending spiral of destruction […] The chain reaction of evil — hate begetting hate, wars producing more wars — must be broken, or we shall be plunged into the dark abyss of annihilation.

Martin Luther King, Jr. (1929-1968) American clergyman, civil rights leader, social activist, preacher

Strength To Love, ch. 5 “Loving Your Enemies,” sec. 2 (1963)
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