Relation that holds between two temporally simultaneous or successive events when the first event (the cause) brings about the other (the effect). According to David Hume, when we say of two types of object or event that “X causes Y” (e.g., fire causes smoke), we mean that (i) Xs are “constantly conjoined” with Ys, (ii) Ys follow Xs and not vice versa, and (iii) there is a “necessary connection” between Xs and Ys such that whenever an X occurs, a Y must follow. Unlike the ideas of contiguity and succession, however, the idea of necessary connection is subjective, in the sense that it derives from the act of contemplating objects or events that we have experienced as being constantly conjoined and succeeding one another in a certain order, rather than from any observable properties in the objects or events themselves. This idea is the basis of the classic problem of induction (induction, problem of), which Hume formulated. Hume's definition of causation is an example of a “regularity” analysis. Other types of analysis include counterfactual analysis, manipulation analysis, and probabilistic analysis.