He argued in 1785 that "cruelty to animals is contrary to male's duty to himself, since it deadens in him the feeling of sympathy for their sufferings, and thus a normal tendency that may be very valuable to morality in relation to other human beings is weakened."[31] 18th century: http://body-detox-soak48259.tinyblogging.com/The-Basic-Principles-Of-outerspace-23114687