If you were to build a philosopher in a laboratory, you would end up with John Stuart Mill.

Born in 1806, Mill was the subject of a rigorous educational experiment conducted by his father, James Mill, and the philosopher Jeremy Bentham. He was not allowed to play with other children. Instead, he learned Greek at age three, Latin at age eight, and was dissecting complex economic theory by the time most kids were learning to jump rope. He was designed to be the perfect “Utilitarian Logic Machine.”

Predictably, this led to a massive nervous breakdown at the age of twenty. He realized that while he was an intellectual giant, he was an emotional void. He eventually cured his depression by reading the poetry of Wordsworth, proving that sometimes the only cure for excessive logic is a bit of romantic wandering.

The Quality of Pleasure

Philosophically, Mill is best known for refining Utilitarianism. His mentor, Bentham, argued that “happiness” was a simple math equation: the greatest good for the greatest number. To Bentham, the pleasure of playing a game of push-pin was equal to the pleasure of reading poetry, provided the intensity was the same.

Mill, having recovered from his breakdown, argued that this was nonsense. He introduced the distinction between Higher and Lower Pleasures.

He famously stated, “It is better to be a human being dissatisfied than a pig satisfied; better to be Socrates dissatisfied than a fool satisfied.” He argued that intellectual and moral pleasures (reading, debating, helping others) were intrinsically more valuable than physical ones (eating cake, sleeping). It was a necessary update that saved Utilitarianism from being a philosophy for hedonists.

The Harm Principle

His most enduring political contribution comes from his essay On Liberty. Here, he articulates the Harm Principle, which remains the bedrock of modern liberal democracy.

The principle is deceptively simple: The only purpose for which power can be rightfully exercised over any member of a civilized community, against his will, is to prevent harm to others.

This means you can shout, drink, be weird, and have terrible opinions, as long as you aren’t physically hurting anyone else. Mill was the ultimate champion of eccentricity. He believed that society needs “experiments in living”—weirdos and non-conformists who test out new ways of being—because that is how progress happens. He feared the “tyranny of the majority” just as much as he feared the tyranny of a king.

The Radical Partner

Mill was also a feminist long before it was fashionable. Influenced heavily by his wife and intellectual partner, Harriet Taylor Mill, he wrote The Subjection of Women (1869).

At a time when women were legally considered the property of their husbands, Mill argued that the legal subordination of one sex to the other was a moral abomination and a massive waste of human talent. He was the first Member of Parliament to call for women’s suffrage. It was a stance that earned him mockery at the time, but history has vindicated him as one of the few Victorian men who actually listened to his wife.

The Human Algorithm

Ultimately, Mill represents the bridge between cold logic and human empathy. He started as a calculator but ended as a humanist.

He taught us that freedom of speech is not just a right, but a necessity for finding the truth (since even wrong opinions force us to clarify why we believe what we believe). He is the patron saint of the open mind, the man who argued that we should never silence a dissenting voice, because there’s always a slim chance that the dissenter might be right and the rest of us are wrong.