There are few political scientists who can claim to have come up with an idea that has shaped real-world politics. G John Ikenberry, a professor at Princeton University, is a member of that small group. Together with his colleague Daniel Deudney, he coined the notion of a “liberal international order” in 1999. Within a few years, the phrase had been adopted by the western foreign-policy elite as shorthand for the world they were seeking to build and defend.

For Ikenberry, the idea of a liberal international order describes a situation in which powerful countries agree to work together, in their mutual interests, through international institutions. It is a world in which principles like open trade and international law are firmly embedded.

Twenty years ago, that sounded like both a reasonable description of how global politics and economics were operating — and a plausible aspiration for how emerging challenges, such as climate change, should be dealt with.

But the past five years have not been kind to believers in a liberal international order. In different ways, both the US and China have turned against the concept of international co-operation. During the Trump administration, the US pulled out of a number of international organisations and accords — such as the World Health Organization and the Paris Climate Accord — and launched a trade war on China. Beijing, for its part, took an increasingly unilateral and aggressive approach to security issues, from the South China Sea to the Himalayas.

The idea of a liberal international order has also come under sustained ideological attack from three directions — the nationalist right, the “anti-imperial” left and from illiberal nations outside the west. For “America First” nationalists, grouped around President Donald Trump, liberal internationalists are simply “globalists” who had sold out US interests. For the left, meanwhile, the current world order is associated with the defence of an exploitative neoliberalism, and with an international power structure with its roots in the age of imperialism. Parts of this critique have also been adopted by nationalists in China, Russia and elsewhere, who argue that the liberal world order is just code for American hegemony.

In response to this formidable political and intellectual assault, Ikenberry has produced A World Safe for Democracy, a thoughtful and profound defence of liberal internationalism — both as a political philosophy and as a guide to future actions. By tracing the evolution of liberal internationalism over the course of two centuries, he demonstrates that this is a set of ideas with deep historical roots, rather than triumphalist fluff produced after the west’s victory in the cold war.

For Ikenberry, the ideas of international co-operation, law, open trade and democracy have followed a “crooked trajectory” throughout history, advancing at times — but also experiencing many trials and setbacks. The point is made by the cover illustration chosen for the book: a picture of St Paul’s Cathedral, surrounded by the smoke of bombs, during the second world war.

Liberalism has survived these trials partly because it is an adaptive and resilient creed — and partly because international co-operation between nations remains necessary. Even ardent nationalists are likely to have to return to the idea because the alternatives are endless conflict or isolation.

Nonetheless, A World Safe for Democracy does more than simply restate the old verities. Ikenberry knows that liberal internationalists need to learn some lessons from the setbacks of recent years — and he proposes some modifications to the creed.

One of his most significant arguments is that, in the west, liberal internationalism has only prospered in alliance with a domestic counterpart. But that alliance has been ruptured by unfettered globalisation — which is perceived to have undermined living standards and social safety-nets in the west. That suggests that future American governments are going to have to be more cautious about free trade. This is no small adjustment because, as Ikenberry demonstrates, support for free trade has been a core commitment of liberal internationalists stretching back into the 19th century.

Another crucial issue that the author grapples with — without fully resolving — is the question of support for democracy around the world. Many liberals are now disillusioned with the crusader version of democracy promotion in which the US and allies attempt to export democracy to much poorer countries, even by force of arms. But Ikenberry thinks that liberal internationalists cannot be indifferent to the fate of political freedom around the world. As he sees it, the “world safe for democracy” promoted by US president Woodrow Wilson in 1917, was primarily a defensive concept. Wilson believed that democracies could only protect their domestic freedoms, if they paid attention to the broader international environment. A world in which tyranny is advancing is unlikely to be a hospitable environment for liberalism — either at home and abroad.

Seen in that light, the effort to construct and defend a liberal international order is not an act of starry-eyed idealism. It is a necessary and pragmatic effort to defend freedom, prosperity and peace.

A World Safe for Democracy: Liberal Internationalism and the Crisis of Global Order, by G John Ikenberry, Yale, RRP$30/£20, 408 pages

Gideon Rachman is the FT’s chief foreign affairs columnist

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