Abstract: Commentary on Shepherd's defense of the Causal Principle (CP) makes the following assumptions. First, Shepherd does not mean what Locke, Berkeley, or Hume mean by "action." Second, Shepherd adopts a substance-mode ontology exclusively to defend CP. I reject both assumptions. Once they are set aside, a picture emerges according to which an object beginning to exist uncaused involves the contradiction of conceiving an unchanging change.

Rather than meaning power or capacity, Shepherd uses "action" like her predecessors to mean a change to an object's qualities. Beginning to exist uncaused is a change to an object not yet in being. When she says that such a change is a quality of the object, Shepherd means that it is among the object's intrinsic properties. That's because by hypothesis no other objects exist to confer extrinsic properties on the new object. The only possible changes are to the object's intrinsic properties. Yet for that object to change, it must exhibit qualities that it does not yet have.

Why should anyone find this convincing? Consider the second assumption among commentators that Shepherd adopts a substance-mode ontology exclusively to defend CP. On that assumption, changing from nonexistence to existence is a quality inhering in a substance that must exist for qualities to inhere in it; but which cannot exist before its existence begins. Hume would dismiss talk of substances as begging the question against him. He defines an object as a bundle of qualities. Shepherd herself defines an object as a mass of qualities rather than a substance in which qualities inhere. Why would she temporarily assume a substance-mode ontology that both she and Hume reject? And how would Shepherd's defense of CP unfold if objects are assumed to be masses of qualities rather than substances?

Beginning to exist is a change wherein an object has a new quality—existence—that it previously lacked. According to Hume, existence is a relation—i.e., an extrinsic quality of objects. Relations require at least two relata. In Shepherd's thought experiment, the first relatum cannot be nothing, and it cannot be empty space, because we cannot have ideas of such according to Hume. Yet Hume thinks we can have an idea of an object as nonexistent. Thus, the first relatum is the idea of a nonexistent object, and the second relatum is the idea of the same object existing.

Here is the problem. A change involves a new intrinsic quality of the object. The only possible new quality would be existence, and Hume thinks that existence is an extrinsic quality. But again, there are no other objects to confer extrinsic qualities on the new object. Thus, there is no change—no action—contrary to hypothesis. On this reading, Shepherd does not beg the question against Hume.