WHEN Gordon Brown went on holiday last summer, depressed after his bruising leadership battles with Tony Blair, he sought comfort in a little light reading. The Roads to Modernity: The British, French, and American Enlightenments, by the neoconservative American intellectual Gertrude Himmelfarb, who argued that the British Enlightenment, with its emphasis on social virtue and compassion, was more admirable than the French and an inspiration to the American. Brown considered this a brilliant book.

Even in London, Brown devours books as voraciously as Charles Clarke eats pizzas. Almost all are works of political or economic philosophy, and most are American. While other politicians’ views tend to be influenced by the writers who inspired them in their youth, Brown’s are constantly evolving in line with new thinking. In his field, he is a rare and genuine intellectual.

Blair, by contrast, enjoys reading history and political biography on holiday, yet the Prime Minister has neither Brown’s rigour nor his appetite for closely argued philosophical tracts. As a result, his political positions are inspired more by Christian morality and an intuitive grasp of human nature than by theory or ideology.

The closest that Blair comes to having a philosophical inspiration is the Scottish philosopher, John Macmurray, to whose work he was introduced at Oxford by his mentor, the Rev Peter Thompson. Thompson lived out Macmurray’s theory that an individual could be defined only by his or her relationships with other people.

“If you really want to understand what I’m all about,” Blair said when he was elected leader in 1994, “you have to take a look at a guy called John Macmurray. It’s all there.” And sure enough, Macmurray’s philosophical mantra is encapsulated in the new Clause 4 of Labour’s constitution, drafted by Blair: “By the strength of our common endeavour we achieve more than we achieve alone.”

Macmurray’s writings dovetailed with the action-based Christianity that Blair was learning from Thompson. “My Christianity and my politics came together at the same time,” he has since explained. “There seemed a coincidence between the philosophical theory of Christianity and left-of-centre politics . . . they were influences that stayed with me.”

This Christianity was an optimistic, inclusive creed. There was nothing that could not be achieved with enough enthusiasm, belief and energy; goodwill and altruism could turn enemies into friends.

While the Prime Minister’s father was an atheist and the young Blair embraced Christianity only at university, Brown was steeped in it from birth. The son of a Church of Scotland minister, he attended Church four times a day every Sunday and listened to his father preach. His Christian tradition embraced the Calvinist emphasis on work, struggle and evils to overcome.

So how do these differing influences and approaches reveal themselves in the two men’s attitude to policy?

Poverty: both men are keen to tackle it. Brown believes in the redemptive power of work, a legacy of his Calvinist upbringing. His tax credits are aimed at making work pay. Blair slightly resents the cost of this and would rather spend the money on improving education and health. But he also approves of forcing people to take work rather than benefits, because it fits in with his belief in “rights and responsibilities”.

Public services: Blair is keener on markets and choice than Brown is, although the Chancellor has been impressed by arguments in favour of the importance of greater individualisation of services and products. Blair has reached the same conclusion without reading books. But the two men have fallen out over the cost of providing more choice: to offer choice, you have to have spare capacity, whether in hospitals or schools. Brown would prefer to spend that money on more nurses or teachers.

When it comes to introducing more market mechanisms into public services, Brown is even more hostile. In his Social Market Foundation lecture two years ago, he argued that there were limits on the use of the market in health. Blair says: “Competition works in other areas. Let’s try it in the NHS.”

Tax: Brown believes in sacrifice for the greater good and the redistribution of money from the rich to the poor.

However, his political instincts have led him to realise that it is less unpopular to take a little from each member of the middle class than a lot from each rich person. Blair is desperately wary of alienating the middle-class and would prefer to raise the money from borrowing, not tax.

Europe: here the differences are perhaps the greatest. Blair has a strong sense that Britain’s destiny lies at the heart of the European project. Brown has none of that idealism and believes that, unless both Britons and Europe change, this country cannot play a bigger role in the EU. To that end, he has been encouraging Europe to undergo economic reform.

In the end, though, it is the two men’s characters and predilections that best explain their political differences. Blair uses his emotional intelligence to develop policies based on intuition, which infuriates Brown, who prefers logical analysis. Blair is impatient to get on with reform; Brown insists on working through the detail.

Blair spends his summers in France and Italy; Brown in Cape Cod. And while Blair plays tennis, Brown reads — and reads, and reads.

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