Frank Harvey is to be congratulated for producing an exemplary book. It makes sophisticated use of counterfactual argumentation to challenge the conventional wisdom about the causes of the Anglo-American invasion of Iraq.
For methodological and substantive reasons it should be read by everyone with an interest in foreign policy. Any assertion of cause implies that, ceteris paribus, the outcome in question would not have occurred in its absence. In circumstances where context or the “lessons” of the past are important or determining – which describes most historical events of interest – statistical tests are meaningless as the “cases” that constitute any data set would be neither comparable nor independent. We can only evaluate causal claims through intra-case comparison, of which counterfactual argumentation is a variant. Historical intra-case comparison is possible when we have closely grouped events or decisions in which key features of context are constant. Austro-Hungarian policy in the July 1914 crisis is a case in point. The government had considered war with Serbia on four occasions between 1911 and 1914, but only drew its sword on the last occasion. We can plausibly argue that novel features of context – the nature of the provocation and the absence of Franz Ferdinand from the decisionmaking process — were determining. In most decisions or events of interest we must introduce intra-case comparison through counterfactual experimentation, as Harvey does.