Democracy solves war---robust theoretical and quantitative support .

Toward Synthesis What conclusions should be drawn from the spuriousness and causal arrow critiques, both with regards to academic scholarship and policy? Should political scientists recognize that the theory that democracy causes peace has been empirically disproven, meaning that the theory should be rejected? When considering whether or not to spread democracy, should policy-makers no longer consider the benefit that democratization might spread peace? There is enough evidence to draw the conclusion that joint democracy does cause peace, and that the dyadic democratic peace is a law. None of the spuriousness critiques, though intriguing, have sufficiently withstood scholarly rebuttals to justify dismissing as spurious the very strong correlation between joint democracy and peace, especially given the experimental, case study, and other quantitative observational work that provide support for different elements of the democratic peace argument. That said, the spuriousness critiques suggest possible modifications of the law of the democratic peace, such as perhaps that the democratic peace could be weaker in less-developed regions. Regarding the causal arrow thesis, though there is evidence that peace may cause democracy as well as democracy causing peace, the evidence is much weaker that peace causes democracy but not vice versa. Further, the claim that peace causes democracy but not the reverse contains theoretical inconsistencies. That said, it is of course conceivable that future studies may emerge that cast decisive doubt on the proposition that democracy causes peace. Data collection in international relations is never going to be as decisive in supporting or refuting theory as data collection in fields like physics or chemistry, where highly precise, often non-probabilistic theory permits point predictions that can be tested many times in controlled laboratory settings. It also will not be as decisive as data collection in the medical sciences, where theories are probabilistic but experiments can be conducted on thousands of subjects and repeated dozens of times. That said, the evidence that dyadic democracy causes peace is as strong as the evidence supporting essentially any theoretical proposition in international relations, other than relatively trivial propositions such as that adjacent states are more likely to fight each other than nonadjacent states. Echoing his 1989 assessment, Levy (, p. 587) remarked that in international relations “no one has identified a stronger empirical regularity” (Levy, , p. 587). That is, if the dyadic democratic peace is not a law, it’s as close to a law that we have in international relations, and probably as close to a law as we are ever going to see.