What makes a thinker? It has been argued that thought comes from a non-physical medium such as a soul or immaterial mind. This notion has few advocates in science or philosophy, who endorse a physicalist account of thought as a purely mechanical process. ‘The mechanical mind’ examines thought as activity in the brain and considers the computational theory of thought. There are three motivations for physicalism: its ability to account for the correlations that exist between states of the brain and states of thought; its capacity to account for the causal role of thoughts; and the way it fits into the idea of evolution. What is the computational theory of thought? Can we challenge that theory?