If the effect fails to come about when the entity exerts itself, that shows the entity only seemed to have the power, but did not actually have it.

Reid is clear that power is not the sort of thing that admits of a logical definition. We cannot reduce it to some set of simpler qualities. However, this doesn't mean that we can't say anything about what power is. On the contrary, Reid makes a variety of claims about power. Importantly, he claims that power is the quality that, when coupled with exertion, necessitates a particular effect. Taking a cue from ordinary language, he holds that it is a contradiction to say that an entity has the pow