Criminal history shows us how many torturers of men, and murderers, have first been torturers of animals. The manner in which a nation in the aggregate treats animals, is one chief measure of its real civilization. The Latin races, as we know, come forth badly from this examination; we Germans, not half well enough. Buddhism has done more in this direction than Christianity, and Schopenhauer more than all ancient and modern philosophers together. The warm sympathy with sentient Nature which pervades all the writings of Schopenhauer, is one of the most pleasing aspects of his thoroughly intellectual, yet often unhealthy and unprofitable philosophy.
The Old Faith and the New (Der alte und der neue Glaube, 1872, translated from the 6th edition by M. Blind, New York: Henry Holt & Co., 1873), vol. II, part IV, ch. 71, pp. 59-60.