How, then, shall we sum up in a sentence the principle of our duties to the lower animals? I do not know that it can be better done than in the words of George Nicholson, one of those early pioneers to the influence of whose writings, though now almost forgotten, the cause of humaneness owes so much. "In our conduct to animals," he wrote, "one plain rule may determine what form it ought to take, and prove an effectual guard against an improper treatment of them—a rule universally admitted as a foundation of moral rectitude: Treat the animal in such a manner as you would willingly be treated, were you such an animal." In our dealings with the non-human as with the human race, it is not "charity," or "self-sacrifice," or "mercy" that is required, but simple justice—an insistence on our own duties as on those of our neighbors, a recognition of our neighbors' rights as of our own.
(Henry S. Salt, "The Rights of Animals," International Journal of Ethics 10 [January 1900]: 206-22, at 222 [italics in original; footnote omitted])