“It is the eternal dispute,” wrote 19th-century French historian Albert Sorel, “between those who imagine the world to suit their policy and those who arrange their policy to suit the realities of the world.” Half a century later, the British historian E H Carr elaborated on this dispute. Carr classified the former as “utopians” and the latter as “realists”. Utopians have the world set in theory, to which practice must conform. Realists look at the world as it is, and theory must conform to it. In US foreign policy, utopianism has been long associated with the tradition that began with president Woodrow Wilson at the Versailles Peace Conference in 1919. Wilson rejected the balance-of-power European order that sought peace through the adjustment of power-based interests. Instead, he proposed a peace based on democracy and the self-determination of peoples. He was utopian in the sense that he had a theory, a liberal vision of world order, to which practice and reality must conform. Reality did not conform, however, and the Second World War followed from the First. “Wilsonianism,” as it became known, had failed to end wars. Despite Wilson's failure to combine utopia with reality, Wilsonianism long survived its author in US foreign policy. With the end of the Cold War and the advent of the “end of history” in the 1990s, Wilsonianism informed liberal interventionist discourse in post-Cold War US foreign policy. Between 1990 and 2016, this failed to combine utopia with reality in a liberal world order, however. The starting point of the new US President Donald Trump, is the critique of this liberal order, which he says has horizontally failed to establish a stable world order and has vertically worked only for the benefit of the few in the US. The latter was his critique of former US secretary of state Hillary Clinton's initial approval of the Trans-Pacific Partnership (TPP) trade deal – in other words, that it represented special rather than popular interests. Trump promised to reverse this scenario. In Carr's typology, Trump promised the end of utopia and the advent of power and interest-seeking in US foreign policy. The liberal order is to be abandoned in all respects, starting with liberal interventionist adventures in Kosovo, Iraq and Libya and extending to free-trade agreements such as the North American NAFTA agreement and the TPP. Instead, Trump has called for a power-based approach to the Syrian conflict, emphasising common ground with Russia in fighting the Islamic State (IS) group. He has called for a wall to be built on the US border with Mexico and for fair, not free, trade with states like China. As for NATO and US allies in Southeast Asia, the US has no special obligation to maintain the liberal order, Trump says. The US's European allies, along with Japan and South Korea, also need to spend more money on defence to protect their security interests. Is Trump a realist? In a way his power-based interest approach gives this impression. But given his initial attitude towards Taiwan and his grandiose rhetoric, his realism is not reminiscent of the Nixon-Kissinger era, which promoted détente with the former USSR and opened US relations with China. Given his staunch criticisms of the liberal order, Trump is certainly not a Wilsonian either. Trump is a knight who has ridden the horse of populism better than any other candidate. His gains so far have been more by way of popularity than policy. Take his strategy to tackle unemployment in the US by threatening companies and putting pressure on them not to move their operations off-shore. This is a “fake policy,” writes US commentator Paul Krugman in The New York Times, and one designed only to boost Trump's popularity. The question of popularity aside, the fact is, as the UK magazine The Economist explained recently, that the world is changing. Old-style stable manufacturing jobs are simply no longer available in sufficient numbers. New skills are required for employment. In terms of policy, this requires systemic change, or government investment in new forms of education and lifetime training. The American people want simple answers, and Trump provides them in his tweets. But what happens when such tweeted answers cannot be translated into policy? So far, Trump's approach has been to assign scapegoats, such as Mexican immigrants and China, against which US national interests are then juxtaposed. Just days into the Trump presidency tensions rose with Mexico over a US suggestion to impose a 20 per cent import tax to pay for the wall that Trump wants to build along the Mexican border. Mexican Foreign Minister Luis Videgaray responded by saying that “a tax on Mexican imports to the United States is not a way to make Mexico pay for the wall, but to make the North American consumer pay for it through more expensive avocados, washing machines and televisions.” The truth is somewhere in the middle. The bottom line is that in a global and interdependent world Mexico (or China for that matter) will not suffer alone. Trump's threats need to take into account the truly global character of trade, which when it is hit will not hit back in one place only. The fear in the Trump era is therefore not of a Wilsonian utopia, but of a realism that by putting “America First” defines US national interest too narrowly to be compatible with a globalised world. Realism that is incompatible with the present is indistinguishable from utopia in its refusal to adjust theory to reality. The question is whether the Trump administration will be able to combine utopia with reality in a new world order based on the adjustment of US power and interest with the world. Or will the world continue to experience US utopia in a new age of conflict? One can only hope it is the former and that Trump's rhetoric is designed to boost popularity at home but stops short when it comes to pursuing utopian policy abroad. The writer holds a PhD in international relations and teaches at the University of Leicester, UK.