Counterfactual reasoning is broadly implicated in causal claims made by historians. However, this point is more generally recognized and accepted by economic historians than historians of science. A good site for examining alternative appeals to counterfactuals is to consider "what if" the Scientific Revolution had not occurred in seventeenth-century Europe. Two alternative interpretations are analyzed: that the revolution would eventually have happened somewhere else ("overdeterminism") or that the revolution would not have happened at all ("underdeterminism"). Broadly speaking, these two interpretations correspond to the respective attitudes of philosophers and historians to the development of science. However, a case is presented for syn...