 Indifferent hypotheses are ontological in nature and are, for example, mechanical models of underlying mechanism. As Poincaré emphasizes, these can frequently be exchanged without sacrificing empirical accuracy. Take, for example, the propagation of heat, where “through the effects of the averages and thanks to the medium’s symmetry, all the differences even out” and we need not inquire how each molecule radiates. Such hypotheses are mere tools useful for thought but “unverifiable” and “useless” as such (Poincaré 1902: 169; 2017: 111).