Lewis Gompertz · Public domain

An early and uncompromising voice for animal welfare in Britain, arguing in Moral Inquiries on the Situation of Man and of Brutes (1824) that using animals for human purposes was morally wrong, and living by a diet and lifestyle later recognized as an early form of veganism. A founding member of what became the RSPCA, he served as its honorary secretary until resigning in 1833 over its adoption of an explicitly Christian constitution, then co-founded the Animals' Friend Society to continue the work on his own terms.