Abstract

It is widely believed that Hume recognizes only two types of causality-one equivalent to a constant conjunction between two "objects," the other involving somesort of necessary connection between them. I will refer to these types, respectively, as "conjunction" and "necessity." I believe that Hume relies on a third type of causality-a process by which a constant conjunction of perceptions causes someone to acquire a mental habit. To remain close to Hume's terminology, I will refer to the process as "repetition." The main thesis of this paper is that this process, though causal, cannot be equated with either conjunction or necessity. Repetition is no small matter. It is the key to the correctness of Hume's overall account of causality and causal belief since it explains why humans have causal beliefs,why the causes they believe in need only be revealed in conjoined perceptions, and yet also why humans believe that a cause involves a necessary connection with its effect even though this belief is unverifiable.