Kissinger: The Idealist, 1923-1968. By Niall Ferguson. Penguin Press; 1008 pages; $39.95. Allen Lane; £35.

NOBODY divides opinion like Henry Kissinger. As national security adviser and then secretary of state, under presidents Richard Nixon and Gerald Ford, Mr Kissinger was both a media superstar and disowned by his former colleagues from Harvard. In 1973 he won the Nobel peace prize; yet critics like Christopher Hitchens insisted he deserved to stand trial for crimes against humanity. Mr Kissinger has been lionised as America’s supreme 20th-century diplomat. However, after he left office in 1977 at the age of just 53, no president ever again trusted him with a senior job.

Into this contested ground strides Niall Ferguson, with the first, magisterial instalment of a two-volume biography. Mr Ferguson, a British historian also at Harvard, has in the past sometimes produced work that is rushed and uneven. Not here. Like Mr Kissinger or loathe him, this is a work of engrossing scholarship.

Three conclusions lie at the heart of Mr Ferguson’s analysis. The first, and the bravest, is that the period before Mr Kissinger became a statesman is worth a volume all to itself. That turns out to be inspired. It creates room for a harrowing account of the Nazis’ indoctrination of Fürth, the Kissingers’ hometown in Bavaria, and the deepening persecution that so much of its Jewish population, including Mr Kissinger’s father, found almost impossible to comprehend. Mr Ferguson goes on to describe Mr Kissinger’s intellectual development after the second world war. Here, seen through the letters, articles and books of a first-class mind, is a gripping commentary on the geopolitics of the 1950s and 1960s, including the quagmire in Vietnam and the struggle with Soviet Russia over Berlin and Cuba.

This leads to Mr Ferguson’s second conclusion: that Mr Kissinger matters because of his ideas. The contrast is with Walter Isaacson’s celebrated biography, which analyses its subject chiefly in terms of his—flawed—character. Because he is concerned with ideas, Mr Ferguson has read Mr Kissinger’s works with great care. He is thus able to skewer simplistic claims that the professor is essentially a devotee of Machiavelli or a simple exponent of the 19th-century European balance-of-power politics that he wrote about.

Instead Mr Ferguson sets out how academic study and experience on the fringes of the Kennedy and Johnson administrations forged the views of government that Mr Kissinger would later carry with him into the White House. Most important is a scathing scepticism of bureaucracies—especially the State Department—because they pursue their own agenda, gravitate towards the middle ground and drown decision-makers in paperwork. Successful government means escaping their influence.

Mr Kissinger came to see statesmen as “tragic” figures, forced to choose between unpalatable alternatives. Decisions are usually best taken early, because incoming evidence continually narrows the options. The tragedy is that nobody appreciates the disasters statesmen avoid. Johnson, for example, would always be blamed for expanding the Vietnam war, but had he abandoned South Vietnam in 1965, as some advised, the dominoes in South-East Asia might have fallen as country after country surrendered to communism.

This focus on ideas leads to the book’s third conclusion. As the title underlines, Mr Ferguson thinks that, during this part of his life, the man usually taken to embody cold-war realpolitik was in fact an idealist. Readers may not be convinced.

To most people, an idealist is someone who stands by a moral principle, come what may. In foreign-policy scholarship, the term is associated with Woodrow Wilson’s notion of subordinating power to international rules. It is not always clear which definition Mr Ferguson is using. At times, he bases his claim for Kissingerian idealism on a highly technical allusion to the moral philosophy of Immanuel Kant. He wins the argument only by turning “idealism” into something that will fully satisfy neither lay nor scholarly readers.

More interesting are the episodes where he cites the principled arguments Mr Kissinger uses against hard-nosed pragmatists—for example, during Kennedy’s presidency, when he called for America to insist that the universal principle of self-determination should apply to Berlin, then partially under Russia’s thumb.

That certainly sounds like idealism. Yet Mr Kissinger understood that the appeal of communism was justice. He believed that to counter it the United States needed to promote ideals of its own. Mr Ferguson never manages to dispel the impression that for Mr Kissinger freedom and self-determination were not sacred principles in themselves, but tools provided by American political culture to be exploited by a ruthless tactician in the contest against revolutionary communism.

Mr Ferguson is able to portray Mr Kissinger as an idealist partly because he has so little to say about the professor’s machinations in the pursuit and manipulation of power. Such behaviour was to be on lurid display in the Nixon White House. The much-awaited second volume will not so easily pass over it.