 Kilvington’s sophisms are meant to be of logical interest, but they also pose important questions in physics or natural philosophy. In constructing his sophisms, Kilvington sometimes makes use of observable physical motion and at other times appeals to imaginable cases that have no reference to outside reality. Although the latter cases are impossible physically, they are theoretically possible, i.e., they do not involve a formal contradiction. At one point he writes, “thus even though the hypothesis supposed there is impossible in fact … it is nevertheless possible per se; and for purposes of the sophisma, that is enough [unde licet casus idem positus sit impossibilis de facto … tamen per se possibilis est; et hoc sufficit pro sophismate]” (S 29: 69; tr. Kretzmann and Kretzmann 1990b: 68).