Causal processes contrast with pseudo-processes which lack the ability to transmit marks.
Spatio-temporally continuous causal processes that transmit marks as well as causal interactions are at work when male Mr. Jones ingests birth control pills the pills dissolve, components enter his bloodstream, are metabolized or processed in some way, and so on.
CpG islands were also discovered to be important for transmitting epigenetic marks (that is, for transmitting heritable information that does not depend on the DNA itself; Mohandas et al., 1981; Li et al., 1993).
A process is capable of transmitting a mark if, once the mark is introduced at one spatio-temporal location, it will persist to other spatio-temporal locations even in the absence of any further interaction.
It seems desirable, therefore, to abandon the requirement that a causal process is one that is capable of transmitting a mark in the absence of further interactions.
Firstly, there are cases where pseudo processes qualify as being capable of transmitting a mark, because of the vagueness of the notion of a characteristic.
To begin with, a process may be a causal process even if it does not in fact transmit any mark, as long as it is true that if it were appropriately marked, it would transmit the mark.
Editorial judgment will be influenced by the presumed needs of readers: in an edition intended for scholars, very corrupt passages are often printed as transmitted and marked with a dagger, whereas in an edition for the student or general reader some compromise may be accepted in the interests of readability.
Thus for Salmon a causal process is one which can transmit a mark, and it is these spatiotemporally continuous processes that propagate causal influence.
We should note for future reference that, as characterized by Salmon, the ability to transmit a mark is clearly a counterfactual notion, in several senses.
