One can generally say this about men: that they are ungrateful, fickle, simulators and deceivers, avoiders of danger, greedy for gain; and while you work for their good they are completely yours, offering you their blood, their property, their lives, and their sons when danger is far away; but when it comes nearer to you, they turn away.
cruelty to animals is contrary to man's duty to himself, because it deadens in him the feeling of sympathy for their sufferings, and thus a natural tendency that is very useful to morality in relation to other human beings is weakened.
'Thou shalt not kill' does not apply to murder of one's own kind only, but to all living beings and this commandment was inscribed in the human breast long before it was proclaimed from Sinai.