He threatened Gauguin with a razor the same night he cut off part of his own ear
[Archive] - Straight Dope ... [PAR] We can't know for certain what drove Van Gogh to do what he did, but persons .... 
in a quarrel in which van Gogh wildly threatened Gauguin with a razor; the same 
night, in deep remorse, van Gogh cut off part of his own ear.