One viewpoint on this question is that cause and effect are of one and the same kind of entity, with causality an asymmetric relation between them. That is to say, it would make good sense grammatically to say either ""A" is the cause and "B" the effect" or ""B" is the cause and "A" the effect", though only one of those two can be actually true. In this view, one opinion, proposed as a metaphysical principle in process philosophy, is that every cause and every effect is respectively some process, event, becoming, or happening. An example is 'his tripping over the step was the cause, and his breaking his ankle the effect'. Another view is that causes and effects are 'states of affairs', with the exact natures of those entities being less restrictively defined than in process philosophy.