 More precisely, Putnam sketches his earliest account in terms of Turing Machines (TMs) only, appealing to the “machine tables” that are a standard way of defining specific TMs. A machine table consists of one column for each of the (finitely many) internal states of the TM and one row for each of the machine’s symbol types. Each entry in the machine table specifies what the machine does given the pertinent symbol and internal state. Here is how Putnam explains what it takes for a physical system to be a TM: