Steven PinkerSteven Pinker is a psychologist and prolific writer who occasionally comments on free will. In his 1997 How the Mind Works, he condensed the standard argument against free will into a single sentence,
"a random event does not fit the concept of free will any more than a lawful one does, and could not serve as the long-sought locus of moral responsibility." (p.54)Pinker is a strong supporter of the "computational theory of mind," his "recurring metaphor of the mind as machine." This is the idea in cognitive science that we can learn a great deal from computing machines about intelligence and the reasoning processes in our minds. He examines alternative explanations for intelligence.
The traditional explanation of intelligence is that human flesh is suffused with a non-material entity, the soul, usually envisioned as some kind of ghost or spirit. But the theory faces an insurmountable problem: How does the spook interact with solid matter? (p.64) Another explanation is that mind comes from some extraordinary form of matter. Darwin wrote that the brain "secretes" the mind, and recently the philosopher John Searle has argued that the physico-chemical properties of brain tissue somehow produce the mind just as breast tissue produces milk and plant tissue produces sugar... Intelligence has often been attributed to some kind of energy flow or force field. Orbs, luminous vapors, auras, vibrations, magnetic fields, and lines of force figure prominently in spiritualism, pseudoscience, and science-fiction kitsch. The school of Gestalt psychology tried to explain visual illusions in terms of electromagnetic force fields on the surface of the brain, but the fields were never found. Occasionally the brain surface has been described as a continuous vibrating medium that supports holograms or other wave interference patterns, but that idea, too, has not panned out. The hydraulic model, with its psychic pressure building up, bursting out, or being diverted through alternative channels, lay at the center of Freud's theory and can be found in dozens of everyday metaphors: anger welling up, letting off steam, exploding under the pressure, blowing one's stack, venting one's feelings, bottling up rage. But even the hottest emotions do not literally correspond to a buildup and discharge of energy (in the physicist's sense) somewhere in the brain. (p.65)Pinker concludes that none of these is a successful explanation, then offers one that focuses on the abrstract idea of information, which leads him to his metaphor of the mind as an information-processing machine, a biological Turing machine (or virtual mental computer).
No, intelligence does not come from a special kind of spirit or matter or energy but from a different commodity, information. (p.65) Does this mean that the human brain is a Turing machine? Certainly not...other kinds of symbol-processors have been proposed as models of the human mind. These models are often simulated on commercial computers, but that is just a convenience. The commercial computer is first programmed to emulate the hypothetical mental computer (creating what computer scientists call a virtual machine), in much the same way that a Macintosh can be programmed to emulate a PC. Only the virtual mental computer is taken seriously, not the silicon chips that emulate it. Then a program that is meant to model some sort of thinking (solving a problem, understanding a sentence) is run on the virtual mental computer. A new way of understanding human intelligence has been born. (p.68-9)Abstract information is neither matter nor energy, yet it needs matter for its concrete embodiment and energy for its communication. Information is the modern spirit, the ghost in Pinker's machine.