 Given that Hobbes was convinced of the impossibility of knowing the actual causes of natural phenomena, he held that any phenomenon admits of multiple possible explanations. This should not be taken to imply that Hobbes saw all explanations, and thus all possible causes or suppositions, as standing on equal footing. Instead, Hobbes held that work in first philosophy and geometry must be completed prior to attempting to make any explanations in natural philosophy. This seems to be what Hobbes meant when he said that “nothing can be demonstrated by physics without something also being demonstrated a priori” (MC 42; OL II.93). When giving an explanation, Hobbes held that one should ideally appeal to those causes that are demonstrable from geometry when mixed with facts and rule out those that are not intelligible according to geometrical principles.