The dominant scientific and philosophical view of the mind -- put starkly, that cognition is computation -- is refuted herein, via specification and defense of the following new argument: Computation is reversible; cognition isn't; ergo, cognition isn't computation. The specification of the argument involves a quartet: (i) certain elementary theorems from computability theory, according to which computation is reversible; (ii) the doctrine of agent materialism, according to which, contrary to any sort of dualistic view, human agents (= human persons) are physical things whose psychological histories are physical processes; (iii) the introspection- and physics-supported fact that human cognition is not reversible; and (iv) the claim -- fundamental to AI and Cognitive Science, and, again, put roughly for now -- that cognition is computation. The basic structure of the argument is straightforward: the conjunction of (i), (ii) and (iii) entails the falsity of (iv).
Our plan is as follows. In Section 2 we take some preliminary steps toward unpacking the ``cognition is computation" slogan. In Section 3 we provide a rudimentary but sufficient-for-present-purposes account of recursion-theoretic reversibility. In Section 4 we present the Argument From Irreversibility. Section 5 is a sustained dialectic arising from objections to the argument -- a dialectic which generates specification of the argument presented in Section 4. In the final section, 6, we express our intuitions about what should supplant the view that cognition is computation, and by doing so offer a glimpse of our forthcoming monograph on ``uncomputable cognition" [2b].