It is the objective of this paper to point out that discussions about cause and effect, and particularly those which bear upon their temporal relationship, are often blurred by failure to make use of the time-honored distinction between transeunt and immanent causes. Transeunt causes are in evidence whenever we discern two systems, S1 and S2, spatially separated, but locked in interaction. In this perspective, cotemporaneous changes can be asserted both of S1 and S2. S1 has an effect on S2, and (...) vice versa. Both effects take place simultaneously but are, as a rule, of different nature. Whether we read the causal relationship from S1, as the cause, to the changes of S2, as the effect, or the other way, from S2 to S1, depends on nothing more objective than the momentary direction of our interest. Immanent causes get into focus whenever we compare the internal conditions C1 and C2 which characterize a system S0 at two different moments t1 and t2. If t1 is earlier than t2, there is a sense in which we can say that C1 is a cause, and C2 its effect. (shrink)