The “most open-minded man in England”, Gladstone called him. John Stuart Mill, like Shakespeare and Dr Johnson, is someone we like to hold up as the essence of Englishness. Since his death in 1873, much of his philosophy and economics has been absorbed or superseded, but On Liberty and The Subjection of Women, those two cornerstones of liberal thought, seem more resonant and provocative than ever. Whether the nation is fretting about cartoons of the Prophet Mohammed, the wearing of the hijab or the rights of consenting adults to hammer nails through their genitalia – in short, wherever individual freedom is definedor defended – Mill is sure to be claimed by one side or another. During the debate on the ban on smoking in public places, Mill’s famous harm principle (“The only purpose for which power can rightfully be exercised over any member of a civilised community, against his will, is to prevent harm to others”) was cited by both camps. He would surely have been delighted.

High time, then, for a new biography, since there have been virtually none since 1954 save Nicholas Capaldi’s error-filled argument for Mill as neocon. Richard Reeves, a political journalist with new Labour links, seems to grind no party-political axe. This biography dispassionately presents the richness and contradictoriness of Mill’s theories, and skilfully shows the way in which his integrity forced him to modify them in the light of his experience. Unlike most pontificaters on justice, Mill actually lived what he preached.

Mill was born in 1806 into the creed of Utilitarianism, co-founded by his father James, who famously educated him at home. Before the age of six, Mill had written a history of Rome; at seven he was reading Plato’s dialogues in Greek; at eight he was adept in Euclid and Demosthenes. Yet, he said later, he ended up feeling like a well-equipped ship that could not move. Utilitarianism, designed to promote general happiness, was just a dry calculation of pleasure units that sapped his capacity for pleasure. His father (the model for Dickens’s Gradgrind) considered poetry the “expression of barbarous people before they can speculate”.

Ultimately, it was through reading Wordsworth and other nature poets during a “mental crisis” in his early twenties that Mill first learnt to feel, and broke free of his father and his upbringing. The refined version of utilitarianism he produced in 1863 upheld self-cultivation, spiritual development and purposeful autonomy over the piggishness of “lower pleasures” — and therefore barely counts as utilitarianism, in which all pleasure-causing things are necessarily on a par.

Wordsworth was an apostate from radicalism, and Mill lost friends by espousing him and the reactionary Thomas Carlyle, whom later he bitterly opposed over slavery and Governor Eyre’s suppression of Jamaican rebels. Antagonising radicals and reactionaries alike by his articles and editing in the London and Westminster Review, Mill was a sole voice of English support for the French revolutionary government in 1848, yet considered suffrage for the illiterate a “false democracy” likely to foment “the selfishness and brutality of the mob” until they were properly educated and unless they could vote for leaders more virtuous and intelligent than themselves.

It is not surprising that Mill is claimed by every shade of the political spectrum from socialist left to libertarian right, for he wonderfully eluded dogma and predictability. Although he has been criticised by no less an authority than Gordon Brown for his “extreme view of liberty” and “crude libertarianism”, Mill’s thought, as shown here, was anything but crude. It is not mere freedom from constraints — the negative liberty dear to libertarians — that he wanted, but “positive liberty”, the freedom that goes with virtuous conduct, appreciation of the arts, intellectual debate. Eager for universal education, he was at the same time wary that it would foster “collective mediocrity” at the expense of genius. How he would have hated our current education system in which students are fobbed off with eighth-rate “relevant” material, pumped with digests of set texts, in case the originals are too difficult, and spoon-fed the arguments for and against any issue to regurgitate in their exams.

Mill is often accused of priggishness and “preachiness”, of being one of Hegel’s “Beautiful Souls” (“Ah, the finishing governess,” murmured Disraeli when Mill rose for his maiden speech as a Liberal MP). But Reeves is keen to present him as the firebrand he seemed to so many of his contemporaries. The relationship with Harriet Taylor, whom Mill met at 24, was one of the great, and shocking, Victorian love stories. “Pale and passionate and sad-looking, a living romance heroine” (in Carlyle’s words), Taylor was an intellectual whom Mill, with astonishing generosity, credited with “joint production” of much of his best work. She was already married, and the couple kept up a semblance of propriety for 20 years. Although they often went on holiday together, and Mill regularly dined at the Taylors’ house while Mr Taylor went to his club, they claimed that their companionship was celibate, about which Reeves is politely sceptical. When Mr Taylor died, they married, even though they had always declared wedlock illiberal. Mill drew up a document beforehand expressing his disapproval of marriage and promising never to use the “odious powers” it gave him.

Mill believed in fierce debate to ensure that opinions were not held “only by accident” but with “a complete conviction” — not out of regard for self-fulfilment per se, or diversity of opinion, but because opposing doctrines could contain “half-truths”. For Mill, says Reeves, “the truth was real and solid — it was just that under typical circumstances, different individuals or factions captured a portion of it”.

He tried to reconcile Romanticism with the Enlightenment, socialism with liberalism, fairness with elitism. Impossible projects, but, in a lucid, balanced, understated way, Reeves shows us how brilliantly they fail.

John Stuart Mill: Victorian Firebrand by Richard Reeves

Atlantic £30 pp616

Available at the Sunday Times Books First price of £27 (including p&p)

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