 Salmon deemed a decisive advantage of conserved quantities over mark transmission the fact that causal processes are defined in terms of characteristics they actually possess, rather than of their capacity to transmit marks. This makes it unnecessary to appeal to counterfactuals. Moreover, the conserved quantities approach allows one to handle intersections that are untreatable by the mark method, such as those of Y and \(\lambda\) types. These obtain whenever two processes merge into one—for instance, when a snake swallows a mouse—or two processes emerge from one—for instance, when a single-celled organism splits into two cells. A major difference with Dowe’s approach is Salmon’s insistence upon causal transmission, as opposed to the mere possession of conserved quantities, so that “a process is causal if and only if it transmits a conserved quantity” (Salmon 2010: 10; see also Salmon 1997). The capacity to transmit conserved quantities provides an easy way to distinguish causal from pseudo processes, which do not have that capacity. The at-at theory of transmission is retained, to mean that a conserved quantity “is at the appropriate place at the appropriate stage in the process” (Salmon 2010: 10). The mark method keeps an important role as a tool for detecting causal relationships.