Our definition of an action in Chapter 1 tells us how to select from among canonical personal-event-designators those that designate actions. But to know what makes an action-designator is not yet to have a complete understanding of what makes an action. For canonical action-designators are not correlated one to one with actions. Distinct designators do not always designate distinct actions. For example, it is natural to think that although «S's willing to exert force with her hand at t» and «S's raising her hand at t» designate distinct actions, «S's raising her hand at t» and «S's slowly raising her right hand at t» designate the same action (given that each of these designators is canonical and thus uniquely picks out a single action). But our criterion for picking out action-designators does not tell us what guides such a judgment. This chapter takes up the task of developing a criterion for deciding when distinct (canonical) action-designators designate distinct actions.

We need to be concerned here only with designators in which the type of the action designated is made fully explicit. Consider a designator of the form «S's doing this morning the same thing she did yesterday that R complained about», one that uniquely picks out a particular action. It picks it out as being of a certain type (the type S did yesterday that R complained about), but it does not, just in virtue of its content, tell us what that type is.