Jeremy Bentham was an English philosopher, jurist, and social reformer regarded as the founder of modern utilitarianism. He was an atheist and an early advocate for granting moral consideration and rights to non-human animals based on their sentience, not on capacity to reason.

He wrote in 1780: “The day may come when the rest of the animal creation may acquire those rights which never could have been witholden from them but by the hand of tyranny… The question is not ‘Can they reason?’ nor, ‘Can they talk?’ but, ‘Can they suffer?'”

Bentham on Wikipedia