The second part shifts focus towards embedding mathematical explanations within a framework of counterfactual reasoning. This chapter sets up the context. It discusses a proposal for a non-interventionist counterfactual account for explanation. If the counterfactual information can indeed be separated from the causal information, then mathematical explanations could in principle be incorporated into a counterfactual theory of explanation. Because this inevitably leads to impossible antecedents, as mathematical properties are necessary, the topic of counterpossibles is introduced, specifically with regard to the question whether they are trivially true.