Fear is not only a potent force in international relations today - it has a distinguished pedigree in the study of international politics.

Thucydides' history of the Peloponnesian War, often claimed (perhaps dubiously) as a precursor to modern political science, sets forth the famous trilogy of motives said to compel states both to their imperial heights and bring them to their inevitable debasements: fear, honor and interest. But fear, not glory or gain, is the leitmotif of the untitled narrative. Thucydides deems Spartan alarm at Athens' blooming maritime empire to be the "truest cause" of the twenty-seven year war that tore Ancient Greece to shreds. His Athenian characters argue that their empire was driven not by pecuniary motives but fear, and others would have acted identically. Little wonder, then, that this two and a half millennia-old account of a regional conflict resonated so sharply in the panic-gripped America of the Cold War, fixated on a quasi-Spartan adversary, an autocratic land-power with opaque internal workings and disdain for the individual. It was the terrifying thought of Sputnik and spies that propelled Americans to fling men and materiel across the globe over the subsequent decades.

The English philosopher Thomas Hobbes, who was enamored with Thucydides' political sensibility (and undertook a translation himself), imported wholesale that tripartite psychology. In Leviathan, he argued that of the "three principal causes of quarrel", fear was "the passion to be reckoned upon". But demonstrating the state of nature's full depredations - the poverty, the brutishness, and the whole train of now-hackneyed horrors drawn from the contemporary English Civil War - required invoking politics between polities, the lawless condition in which states dealt with one another. His theoretical edifice pivots on what would later be dubbed the "security dilemma". In the absence of a world sovereign, actions undertaken by one state in its defense are indistinguishable from those directed at harming another, prompting the smallest of disturbances to erupt into an unstoppable arms race.

This notion of a perpetual standoff reached its apogee with the generation of mathematicians-cum-Cold Warriors who drew on game theory to generate lessons for American nuclear strategy. Perhaps most famously, the Nobel Prize winner Thomas Schelling sketched out in the 1950s an extreme form of this dilemma. This was the perverse logic of the "reciprocal fear of surprise attack". "If I go downstairs to investigate a noise at night, with a gun in my hand, and find myself face to face with a burglar who has a gun in his hand, there is danger of an outcome that neither of us desires", since the fear of each that the other would preempt the fear of his opponent would catastrophically multiply. Only a few years later, Soviet rockets would be placed ninety miles from the American mainland, and the academic formalization of fear in fiendishly complex models of political choice would become commonplace.

It is this near-dystopian intellectual tradition, devoid of trust and suffused with danger on a local and global-historical scale, on which the contemporary study of international politics rests today. For many years, the benchmark theory of international politics was that of Kenneth Waltz. Labeled "Neorealism", it spat out two major hypotheses: balances will form, and certain types of balances - above all, multipolar ones - are prone to war. Its notability lay in its parsimony. Whether through alliances or arms buildups, states would balance against those more powerful, regardless of their apparent intentions.

In a seminal article published in the heady days of 1990 titled "Back to the Future", John Mearsheimer (perhaps now more notorious for his co-authorship of the Israel Lobby) pushed this theory to its limits, arguing that "the prospects for major crises and war in Europe are likely to increase markedly if the Cold War ends". For half a century, America's fear of a Soviet-dominated heartland fortuitously led it to suppress the plethora of fears that had bled the continent dry. Germany was protected from the USSR, France and others from Germany, and these interlocking arrangements were formalized in a grand military alliance built from the start on Senator Vandenburg's exhortation that Truman "scare the hell out of the American people". (By mid-1946, this was superfluous anyway: they were already petrified). One of Mearsheimer's scenarios portrayed the "Balkanization of Europe" in which a reunified Germany, absent its American counterweight, would threaten Poland, Czeschoslovakia and Austria. A lumbering, potentially nationalist, Germany would seek nuclear weapons to protect itself from a conventional Soviet attack, and the established nuclear powers could launch either preventive or first strikes.

This dark, even absurd, vision stemmed from the indiscriminate application of the logic of balancing, shorn of Thucydidean nuance. In reality, states patently balance not against the fact of power, but its potentially threatening use. This is not unrelated to power's physical properties, such as proximity and deployment. But it is even more to do with idiosyncratic assessments of intentions. This is the true limitation of the academic study of international politics: political science has been largely unsuccessful in explicating what states do and do not find threatening. We have no "theory of fear".

Perhaps in part as a result, the relationship between the study and practice of international politics has been tenuous at best. The last US Secretary of State, Condolezza Rica, was an expert on the Soviet Union. She famously drew upon her intellectual reserves to state that she was proud of invading Iraq "especially as a political scientist, not as Secretary of State, not as National Security Advisor, but as somebody who knows that structurally it matters that a geostrategically important country like Iraq is not Saddam Hussein's Iraq, that this is a different Iraq under democratic leadership".

Rice's remarks were hardly unscholarly. The discipline really has long claimed that, as a general rule, democracies do not go to war with each other in part because they are not afraid of one another (though few scholars would agree on the reasons for this). If Woodrow Wilson spoke of making the world "safe for democracy", then one (perhaps charitable) reading of the Bush Doctrine was that it aimed at making the world safe with democracy, an awesome and blood-soaked attempt at democracy's selective implantation in a corner of the Middle East. Rice's comments, in other words, are predicated on the notion that autocrats are inherently more threatening to the US than democracies - that we ought to be more fearful of their intentions because of reasons innate to their character.

It is an outstanding historiographical puzzle as to which of Thucydides' three motives drove the events of 2003, but what is certain is that in 2005, 64% of Americans continued to believe that Saddam Hussein had strong links to Al Qaeda. Their overwhelming preference for violent "balancing" is unsurprising: in their case, we can safely surmise that support for the Iraq war was based on politically mobilized fear. Like Truman before him, Bush had scared the hell out of the American people. They came to resent this. We would do well to remember that in the early days of his presidential campaign the now-fading trope of "hope", insufferable and invigorating in equal measure, represented a backlash against what Obama was calling the "politics of fear".

What are we afraid of today - and how can we coolly analyse whether our current fears are well-grounded? The cesspool of international politics offers relatively bottomless supplies of things of which one might easily be scared, though it is difficult to evaluate whether one really should be scared. We have been told with some regularity that the Taliban are poised "sixty miles from Islamabad", that North Korea's new missiles can reach the American mid-west, that Israel is preparing to send nuclear-tipped missiles burrowing into Iran, and the suchlike. Perhaps the biggest elephant - or, rather, dragon? - in the room is the rise of China, reminiscent of Thucydides' reflections on the "truest cause" of his war: "The growth of power of Athens and the alarm which this inspired in Sparta". The analogies fit imperfectly, although like America and the USSR, and America and post-1971 China, Athens and Sparta had previously cooperated to see off a common enemy (the Nazis, Soviets, and Persians respectively).

The American strategic community's occasional paroxysms of fear (you will recall the coming Japanese hegemony of the 1980s) do often subside without causing conflict. But fear is the most visceral of motives, not always subject to placid scrutiny. We abjectly lack any objective way of knowing when fear is warranted, and when it feeds either on itself or the self-serving motives in whose service it has been cynically yoked. The very premise of the academic study of international politics should be to overcome this dangerous limitation.

In the not-too-distant glory days of the Bush administration it seemed as though the partisan use of fear was a potent form of political alchemy. We now know that political alchemy, too, has its limits. But they are limits which are imposed by human actions, not natural laws - and that a better understanding of the role of fear in international politics is a first step towards safeguarding them.


Shashank Joshi researches the role of fear in international relations at Harvard University's Department of Government.