 Salmon explained "causal processes" as "the means by which causal influence is transmitted", and thus what "constitute precisely the objective physical causal connections which Hume sought in vain".Salmon explained that causal processes can transmit a "mark" or can transmit "structure" in a way continuous spatiotemporally.Thereby, the "marking principle" sorts causal processes from "pseudo processes" (Reichenbach's "unreal sequences").