Henry S. Salt 
Animals’ Rights Considered in Relation to Social Progress [EPUB ebook] 

The immediate question that claims our attention is this-if men have rights, have animals their rights also?
From the earliest times there have been thinkers who, directly or indirectly, answered this question with an affirmative. The Buddhist and Pythagorean canons, dominated perhaps by the creed of reincarnation, included the maxim ‘not to kill or injure any innocent animal.’ The humanitarian philosophers of the Roman empire, among whom Seneca, Plutarch, and Porphyry were the most conspicuous, took still higher ground in preaching humanity on the broadest principle of universal benevolence. ‘Since justice is due to rational beings, ‘ wrote Porphyry, ‘how is it possible to evade the admission that we are bound also to act justly towards the races below us?’