“With respect to animal diet, let it be considered, that taking away the lives of animals, in order to convert them into food, does great violence to the principles of benevolence and compassion. This appears from the frequent hard-heartedness and cruelty found amongst those persons whose occupations engage them in destroying animal life, as well as from the uneasiness which others feel in beholding the butchery of animals.”
Observations on Man (1749; 6th edition, 1834), Part II, Chapter III, Section II.
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David Hartley (philosopher) 2
British philosopher 1705–1757Related quotes
"Go Vegan for the Animals" (adapted from "Let’s Talk about Veganism" in Powerful Vegan Messages, 2014), in the American Vegan Society website http://www.americanvegan.org/animals.html.

Veg Family, March, 2003 http://www.vegfamily.com/interviews/ingrid-newkirk.htm

Accepting a Lifetime Achievement Award from In Defense of Animals in 1992.
“Although other animals may be different from us, this does not make them LESS than us”
Source: Animals Matter: A Biologist Explains Why We Should Treat Animals with Compassion and Respect

The Tragic Sense of Life (1913), I : The Man of Flesh and Bone
Context: Man is said to be a reasoning animal. I do not know why he has not been defined as an affective or feeling animal. Perhaps that which differentiates him from other animals is feeling rather than reason. More often I have seen a cat reason than laugh or weep. Perhaps it weeps or laughs inwardly — but then perhaps, also inwardly, the crab resolves equations of the second degree.