 Applying the at-at theory to causal processes having the capacity to transmit marks results in stipulating that the transmission of a mark from a given point A in a process to some point B in the same process simply consists in the fact that it appears at each point between A and B. Incidentally, as observed earlier  (§ 4)  Salmon found Russell’s at-at theory of motion a satisfactory solution to Zeno’s arrow paradox (Salmon 1984: 151–153).