No statue commemorates Richard Haldane, the politician who transformed Britain’s universities and overhauled its army in time for the 1914 war. On his death, Herbert Asquith suggested that he deserved one “struck in gold”, yet the tabloid press had long since toppled the idea. Within months of the war’s start, they had hounded him out of office as a German sympathiser. After all, he had studied there, spoke the language and knew the kaiser.

This first full biography for 60 years, by John Campbell, paints Haldane as a late flowering of the Scottish enlightenment rather than a German stooge. Born and bred in Scotland, he kept a picture of Thomas Carlyle on his desk and wrote a biography of Adam Smith. At 17, he rejected his parents’ religious evangelism and replaced it with a devotion to philosophy, discovered during a six-month spell at the University of Göttingen.

Taking his cue from Hegel and Schopenhauer, Haldane dedicated himself to examining life’s problems from every angle, working out the best solution for society and forging agreement on small, practical steps towards it. He started his career in London and the law, showing an “almost inhuman appetite for work”, which prompted his fiancée to break off the engagement for fear of “intellectual captivity”. He was a bachelor for the rest of his life, although Campbell unearths a tantalising correspondence with Lady Frances Horner, muse to the pre-Raphaelite artist Edward Burne-Jones. Their long relationship, Haldane told her, was “the largest and deepest facet of my life”.

Like many successful lawyers, Haldane moved into politics, becoming a Liberal MP in 1885 at the age of 29, alongside Edward Grey and Asquith. Campbell’s portrait of the trio’s friendship is one of the best passages in the book, their Relugas Compact of 1905 uncannily presaging Tony Blair and Gordon Brown’s Granita Pact of 1994. Neither ended well.

Haldane’s philosophical bent made him more interested than other Liberal politicians in education, which he called “the bedrock of a liberating and constructive citizenship”. A place on the council of University College in London alerted him to the capital’s lack of any university “fit for the metropolis of the Empire”. With Sidney Webb, he gave it first the London School of Economics, then Imperial College. Eventually, Haldane would help to establish many of Britain’s best “red-brick” universities and its adult education sector.

His principal claim to fame rests on his first ministerial job as war minister from 1905-12. The army needed a shake-up after its dismal showing in the Boer War. “We shall now see how Schopenhauer gets on in the kailyard,” exclaimed prime minister Henry Campbell-Bannerman, unsure whether he could combine his philosopher’s idealism with pragmatism. Haldane chose aides with brains and listened to the generals carefully. “The dear generals are angels,” he explained. “I have already made changes which might alarm them and they simply gulp them down.” He turned the army into a rapid-reaction force for overseas deployment rather than for home defence.

Campbell has produced a work of real scholarship. He rejects the traditional chronology to paint a portrait in words, first choosing a broad brush for Haldane’s private life and philosophy, then a finer one for the detail of his career. A disadvantage of this structure is that Horner sadly disappears after chapter three, while Haldane himself first dies in chapter seven (but resurrects).

Campbell sets out to “put Haldane back on the map as a major statesman of continuing relevance”. This advocacy means readers may not discover why Haldane’s colleagues saw him as an “intriguer” or why he forced the illiberal Official Secrets Act through Parliament in 1911. Only historians may see that as a toppling offence; for the rest Campbell makes his case for a statue well, and vacant plinths may soon abound.