Very little of the great cruelty shown by men can really be attributed to cruel instinct. Most of it comes from thoughtlessness or inherited habit. The roots of cruelty, therefore, are not so much strong as widespread. But the time must come when inhumanity protected by custom and thoughtlessness will succumb before humanity championed by thought. Let us work that this time may come.
—Albert Schweitzer, Aus meiner Kindheit und Jugendzeit (1925) in: Ausgewählte Werke in fünf Bänden, vol. 1, p. 305 (S.H. transl.)