  The answer to the first question is quite straightforward. Ockham, like other fourteenth-century theologians  – see, for example,  (Biard 2000) on Buridan – frequently gives instances where we can make reliable causal inferences and come to know causal propositions on the basis of experience (Ockham, Ordinatio Prologue, qu. 2: Opera Theologica I, p. 87) These arguments frequently rely on a theory of natural kinds: for example, Ockham writes