Paradox

220 A BRIEF HISTORY OF THE PARADOXFig. 16.1 Fig. 16.2being, then that computer is a thinking machine. If you area silicon robot that is doing exactly what my carbon-basedreaders are doing, then you are reading my book and havingthoughts about Pascal’s arithmetic machine (one of yourearliest ancestors).Those with lingering sympathy to Descartes believe thatTuring’s emphasis on behavior is refuted by the possibility ofzombies: mindless creatures who are functionally indistinguishablefrom people with minds. Since a zombie is notconscious but can do anything its minded counterpart can do,consciousness does not depend solely on input-output relations.Although the zombie thought experiment is intuitivelypersuasive, functionalists reply that our imaginations arefaulty guides to what is possible. Suppose Pascal’s mechanicalcalculator had three gears aligned as in figure 16.1. It is easyto imagine the gears all spinning. But they are actuallygridlocked.Perhaps you have now rerun the gear thought experimentand have spotted the subtle jam. Now focus your mind’seye on a scenario involving four interlocked gears (fig. 16.2).Still jammed?