 Shepherd does not contend that every change has a cause. The metaphysical structure of a change and that of a cause are entirely different. A change takes place over time and the relation between its earlier and later stages is contingent. Shepherd argues that precisely because Hume supposes that a cause and its effect exist in succession, he precludes their having a necessary or efficacious connection (Bolton 2010: 244). For Shepherd, a change results in a cause if and only if it terminates in a composite efficacious nature that did not exist when the change began. So it might seem that her view cannot account for what Hume purports to explain—the transition involved in a change. 