Jeremy Bentham (1748-1832)

British philosopher and jurist; a founder of utilitarianism. His works include A Fragment on Government (1776) and Introduction to the Principles of Morals and Legislation (1789)
from 'Principles of Morals and Legislation':
The day may come when the rest of the animal creation may acquire those rights which never could have been withheld from them but by the hand of tyranny. . . a full-grown horse or dog is beyond comparison a more rational, as well as a more conversable animal, than an infant of a day, or a week or even a month old. But suppose the case were otherwise, what would it avail? The question is not, can they reason? Nor can they talk? But, can they suffer? Why should the law refuse its protection to any sensitive being? The time will come when humanity will extend its mantle over everything which breathes...