Thucydides attributes the outbreak of the war to “the rise of Athens and the fear this inspired in Sparta.” While pithy, this account raises more questions than it provides answers, epistemologically speaking. Before one can determine what the “cause of a war” might conceivably be in observational terms, it is necessary to define “war” and “cause”.
“War” can be readily defined as inter-state armed conflict. Whether the definition should include economic and cyberwarfare is primarily a definitional issue. Science allows one to posit concepts freely. Operationalizing concepts, that is, determining how concepts translate into observational terms is more difficult. How do we define and recognize states? How exactly should we define inter-state armed conflict (see above)? Does violence have to exceed a threshold? Does conflict have to last a certain minimum amount of time?
But let’s grant that agreement can be found and observational implications be worked out satisfactorily, the much trickier issue of “cause” needs to be defined and nailed down in observational terms. Here are some of the challenges such a task, and any intelligent conversation of the causes of war, faces. First, if a cause is part of the concept of causality, what model of causality do we assume? The regularity , the counterfactual, the mechanistic, the probabilistic or the manipulationist view of causality? And do we want to say that there is a difference between a cause and a reason? And how does one recognize a cause (or a reasons) when one sees one? If we do go with causes (as events), is there a need to differentiate between proximate and fundamental causes? In other words, do we need to conceptualize causal complexity? If so, how do we do that? Is coming to understand (psychologically) more or less satisfactory than to explain an outcome (war)? How do we define “understanding” and “explaining”? No wonder historians often speak of the "origins" rather than the "causes of" or "reasons for" war.
These are challenging, but highly important epistemological and ontological questions. Let’s say we define “reasons” in terms of means-ends-relationship-based goal-directed behavior. What do we say when this goal-directed behavior brings about unintended consequences? Do we say that it was actions of an agent that brought about the outcome, even though the outcome may contradict the original “reason” or motivation? And if we are to define causes as something material or more readily measurable, such as “the rise of Athens,” do we not also need to incorporate the alleged motivation or reason, such as Spartans’ fear to understand (or explain?) war?
What was the reason (or cause?) of the Trojan War? Was it the fact (event) that Helena ran off with Paris? Or was it her husband’s desire to take revenge (or save his honour)? Or was the purported motivation simply a pretext to rally allies and settle geopolitical accounts with the Trojans? (Christopher Marlowe, for one, refused to provide an answer, asking: “was this the face that launched a thousand ships?”). In this case, it will be difficult to avoid an analysis in terms of causal complexity and counterfactuals, perhaps in the context of a mechanistic approach to causality, process tracing and embedded counterfactuals. Should we define reasons as subjective motivation and causes as non-subjective facts or events that lead to (cause?) another events? How explicit do we need to be in terms of embedding the causal analysis of a single case or even a singular event into a broader reference class characterized by probabilistic or non-probabilistic regularity?
And if we do go down the path of reasons, subjectivity and embedded counterfactuals, to what extent is it permissible – in this case – to “anthropomorphize” the state. An important approach to explaining (and predicting) state behavior assumes that the state is a rational, unitary actor with its own reasons and motivations. But is it ontologically legitimate to be so parsimonious as to deny that different decision-making may have different motivations and that state behavior may be as much due to compromise as to systemic pressures?
This, of course, was Graham Alison’s point in his classic The Essence of Decision (1971). State behavior can and sometimes is best explained by organizational or bureaucratic politics. And even if it can be established (in retrospect), what motivated various decision-makers and how policy was shaped by the decision-making process, how reliable should we consider the evidence contained in documents and or expressed in public statements? Are they not likely to at least conceal the true motivation underpinning policies because decision-makers suffer from well-established heuristic and other biases (coherence) and because public statements also need to mobilize domestic constituents in support of war (in case of a decision in favor of war) as well as or justify “just cause” in the eyes of other states, if only strengthen alliances or prevent other countries from supporting their antagonist? Indeed, despite all this talk about the causes of war, research has generated very little actual knowledge.
Recent writing on the causes of war consists of ruminating essays, not rigorous and systematic analyses. Chris Blattmann cites (1) unchecked interests, (2) intangible interests, (3) uncertainty, (4) commitment problems, (5) misperception as reasons for why wars take place. Others add territorial, religious, or nationalist conflict to the list of causes, not to mention imperialism, racism, as well as biological, ethological and psychological causes. It sounds like anything could be a reason and many things could be a cause of war, perhaps including telegrams (Kissinger Diktat)!
More serious approaches to the study of war seek to be more explicit about models, explanations and causality. In Man, the State and War (1959), Kenneth Waltz argues that it is the anarchical nature of the international system rather than the nature of the state or human nature that underpins inter-state conflict and war. This offers a logically consistent account of why wars happen. Empirically validating the model is more difficult, if not impossible, if there is no agreement on how to code cases and measure variables.
Other interesting approaches, such as Stephen Van Evera’s Causes of War (1999) combines theory and evidence to generate middle-range theories. Similarly, rationalist theories seek to account for the so-called ‘war’s inefficiency puzzle. The premise is that military conflict is costly too all parties involved, which should make it more rational to settle conflict without resorting to war. The problem of private information (and the related incentive to misrepresent/ exaggerate one’s power), the commitment problem, and issue indivisibility help account for the occurrence of war. The first problem leads a state to pretend that they are more powerful than they actually are in the hope of a superior non-martial settlement. The second problem is operative even if complete and perfect information is available because of power shifts and the potential incentive for the declining power to launch preventives war in the hope of achieving a more favorable settlement than later on. Finally, if the good that is fought over is indivisible, compromise is impossible.
As Jack Levy put it two decades ago: “Although the field is characterized by enormous diversity and few lawlike propositions, it has made significant progress in the past decade or two: its theories are more rigorously formulated and more attentive to the causal mechanisms that drive behavior.” That is exactly right. Researchers today are more self-conscious about models, explanations and causality. But there is no remotely general theory of the causes war. In fact, there is not even consensus on the causes of specific wars. Look no further than the recent literature on World War One – even though admittedly some accounts have been discredited. True, some accounts have been largely discredits (Fritz Fischer), but the debate continues, as recent works shows (The Sleepwalkers 2013; The Russian Origins of the First World War 2011).
Commentators tell stories and fail to clarify what it is they are saying because they skip over fundamental epistemological and ontological issues, such as what are reasons/ causes and how can one come to know them. If you think about it, there is really very little point in talking about causes (or reasons) unless one clearly defines what they are and what they do (ontology) and how, once they have been defined and operationalized, we can come to know that they were in fact operative (epistemology).
So we are largely forced to listen to (endure!) plausible (non-contradictory) but questionable stories about what causes this war or that. We then often psychologically accept or reject these accounts based on our prior beliefs and cognitive biases as well as our affective attitudes. It largely comes down to individual and social psychology, rather than evaluating hypotheses in light of actual or potential evidence. We would be better off if we were more honest about the ontological and epistemological challenges we face when seeking to establish persuasive accounts of why wars break out. We would be better off if we acknowledged "the clear necessity of explaining historical developments by causes, and the need to take great care, sensitivity, and scrupulousness in deciding what acts as a cause in human affairs, and what acts suffices as evidence of it", in the words of Paul Schroeder. And we would be better off if we were able to force the hedgehogs and talking heads to clarify their ontology and epistemology before telling us what cause of or the reason for a war, or wars, is.