A causal theory of time, or, more properly, a causal theory of spacetime topology, might merely be the claim that according to some scientific theory (the true theory? our best confirmed theory to date?) some causal relationship among events is, as a matter of law or merely as a matter of physically contingent fact, coextensive with some relationship defined by the concepts of the topology of the spacetime. A strongest version of such a causal theory would be one which demonstrated such a coextensiveness between some causally definable notion and some concept of topology (such as "open set") sufficient to fully define all other topological notions. Given such a result, one would have demonstrated that for each topological aspect of the spacetime, a causal relationship among events could be found such that that causal relationship held when and only when the appropriate topological relationship held.