 Putnam considers what is essentially a generalization of the example of the rock from Section 2.2, which was an example of a simple finite automaton transitioning through a sequence of computational states without input or output. An arbitrary physical system that undergoes (possibly continuous) physical transitions can be discretized such that its physical states map onto the computational states of an arbitrary automaton, thus mapping physical state transitions to computational state transitions. Because the physical system and the automaton are arbitrary, every physical system implements every finite automaton.