Minds, Brains, and Science is intended to explain the functioning of the human mind and argue for the existence of free will using modern materialistic arguments and making no appeal to religious concepts. Despite its use of accessible terminology and its straightforward argument, the book is clearly controversial, because Searle attacks dualism, Chomskyan linguistics, behavioralism, cognitive psychology, and the belief in artificial intelligence, all of which have many supporters, both scientists and lay people. At the same time, Searle asserts that human beings have free will, an idea that seems at odds with his materialism, and he does so from a point of view that rejects the dualistic tradition deriving from Rene Descartes, which suggests that the mind is more than the molecular structure of the brain and that free will and determinism therefore coexist. Searle grounds his arguments in appeals to common sense, and readers’ acceptance of them therefore depends on their acceptance of Searle’s examples and analogies.

The first three chapters, which outline Searle’s ideas about the mind-brain / body question and his critique of artificial intelligence and cognitive psychology, depend on a series of analogies. He argues that the relationship of the mind to the brain is like that of a macrocosmic object such as a solid to the microcosmic molecules of which it is constituted; from this analogy, he concludes that the functions of consciousness, intentionality, subjectivity, and mental causation are simply part of the neurophysiology of the brain. He asserts that consciousness exists and that one should accept the fact, rejecting the dualistic idea that the existence of consciousness proves that the mind is more than its material components. He does not, however, provide an analysis of the errors of the Cartesian dualists but simply asserts that their views are incorrect. Furthermore, he does so not from the point of view of philosophers who argue for panpsychism, such as Charles Hartshorne in The Logic of Perfection and Other Essays in Neoclassical Metaphysics (1962), who avoids dualism by attributing intentionality to all physical levels of being, including atoms. Nor does he argue from the point of view of philosophers who avoid both dualism and panpsychism by hypothesizing a hierarchical organization of the universe in which human beings differ from organisms on the other levels. Similarly, Searle begins from a non-transcendentalist position rather than by refuting the position taken by the transcendentalists that mental states are not caused by neurological functions alone.

Searle’s argument that computers cannot think is based on an analogy different from that in chapter 1. In chapter 2, he compares the formal manipulation of symbols by a computer to a man—ignorant of Chinese and left alone in a room— who would be able to produce sentences intelligible to a Chinese speaker by manipulating Chinese characters with the aid of a book of rules. He argues that a computer program merely simulates rather than replicates the functions of the mind and that the program never has semanticity. In addition to showing the limits that he perceives among those who study artificial intelligence, Searle shows the limitations of grammarians, such as Noam Chomsky, who have suggested that the rules of language are merely syntactic.

Searle’s analogy, however, deals only with those mental functions which are involved with the use of language; a reader must extrapolate from linguistics to other mental functions he discusses. Furthermore, a reader must accept Searle’s assumption that the “Chinese room” provides a good analogy for artificial intelligence, a fact which has been questioned by philosophers such as Georges Rey. Finally, although Searle implies that a computer could not be designed with semanticity and that its hardware could not be designed to replicate the biological functions of the brain and therefore produce mental functions, he does not develop his reasons in detail. It is possible to argue that if human beings could produce a perfect duplication of understanding, the replicant would be able to understand.

Acceptance of the second chapter is necessary for acceptance of the third, in which Searle argues that it is a mistake to use the computer analogy to explain the workings of the mind because computers cannot think. He suggests that the computer is neither more nor less exact as a metaphor for the brain than were earlier technological metaphors. His disbelief in the accuracy of the metaphor leads him to question the research carried on by students of cognitivism. Although he demonstrates that the earlier technological metaphors have proved inaccurate, he asserts rather than proves that the computer metaphor is also incorrect, asking his readers to agree that he has discredited an entire field of research.

Chapters 4 and 5, which deal with intentional human actions and the nature of the social sciences, are based on a kind of materialistic but nondualistic reasoning similar to that of the first three chapters. The chapter on intentionality argues that all human actions are intentional and that they can be explained only by reference to mental contexts, conscious or unconscious, a fact which means that “actions differ from other natural events in the world.” Just as his view of the human mind is non-transcendentalist, however, his view of intentionality is that it is not transcendental but separate from causality. He does not clearly state the difference between intentional and psychological states, and his theory of intentionality makes the mind basically self-referential: It is aware of itself and its functions, but since it is a biological phenomenon mental states and the actions dependent on them are subjective. Similarly, in chapter 5 he suggests that the difference between the natural and social sciences is that the former are capable of being explained in terms of generalizations, whereas the latter are capable of being understood only in terms of intentionality. All the social sciences are basically self-referential, because their categories cannot be defined in physical terms and they must be studied in terms of “the intrinsically mental character of social and psychological phenomena.”

The self-referentiality of the human mind, of human action, and of the study of the social sciences leads Searle finally to argue for the existence of free will in self-referential terms. Searle suggests that modern science is incompatible with the traditional doctrine of free will, because true freedom would mean that every person would be capable of changing “the causal order of nature.” Because sciences such as physics have shown that the world is determined by the structure of its molecules and there is no reason to disbelieve the sciences, Searle suggests that it seems improbable that human beings have free will but that it nevertheless exists. Just as a reader who accepts Searle’s premises is likely to agree that the mind exists because of a consciousness of his own mental states, so he is likely to agree that free will exists because a belief in free will is a part of intentionality.

The matter-of-fact tone and the conversational style of the essays make them persuasive even though Searle does not work out all of his arguments with philosophical sophistication. Throughout the six essays, Searle uses analogies to persuade his readers to accept the existence of seemingly incompatible facts without attempting to reconcile them. The book is therefore thoughtful and thought-provoking, leading casual readers to accept both the premises and the views expressed and encouraging others to explore further answers to the questions raised.