John Stuart Mill

Born in 1806, Mill was raised in a controlled experiment by his father, James Mill, and Jeremy Bentham - drilled in Greek at three, Latin at eight, a prodigy built to advance utilitarian philosophy. He suffered a mental collapse at twenty, realizing the system had left him unable to feel, and rebuilt himself by reading poetry and widening his emotional range. He took Bentham's utilitarianism and reshaped it, arguing that some pleasures matter more than others and that liberty itself is essential to human flourishing. On Liberty, published in 1859, laid out the harm principle: the state may interfere with individuals only to prevent harm to others, a line that still anchors liberal thought. Elected to Parliament in 1865, he pushed for proportional representation and became the second MP ever to call for women's suffrage; The Subjection of Women, co-authored with his late wife Harriet Taylor in 1869, made the feminist case in terms his century could hear. He died in 1873 in Avignon, where Harriet was buried, having built the scaffolding on which much of modern liberalism still stands.