Turing Machines and the Mind-Body Problem

Abstract

i In his [1961] Hilary Putnam has argued that 'all the issues and puzzles that make up the traditional mind-body problem ... arise in connection with any computing system capable of answering questions about its own structure'. This shows, he believes, that such issues and puzzles are wholly linguistic or logical in character, and 'have thus nothing to do with the unique nature (if it is unique) of human subjective experience'.1 His argument makes use of the notion of a Turing machine. Such a machine consists of (a) a physical tape, scanner and printing device, along with a control and storage mechanism, and (b) a machine table which comprises a set of instructions for the machine to follow, and which directs the machine to print, erase or move the tape as required. There are thus two kinds of descriptions which can be given of a Turing Machine, the one called its logical description which concerns only the table of rules and instructions and does not presuppose any specific physical embodiment (it may be electronic relays, clerks sitting at desks, or whatever), and the other called its structural or physical description which applies to the specific system chosen to carry out the instructions of the machine table. These two types of descriptions, Putnam goes on to note, are closely analogous to the two types of descriptions typically applied to human beings, namely the psychological and the physical. Thus, the physical description of a human being corresponds to the physical (or structural) description of the machine, and the psychological description corresponds to the logical. A few words of explanation are needed for the second half of this analogy. Putnam makes the following three points in this connection: