Pure deterministic mechanism in consciousness research is in some circles rather out of fashion. Quantum theory (often misunderstood or clouded by unnecessary metaphysical trappings), the increasing use of stochastic models in a wide range of disciplines, the rediscovery of alternative philosophical approaches to logical positivism, and many other influences have tended to displace the clarity of science’s original mechanistic vision without actually supplying a viable alternative. This book argues for a mechanistic approach to the universe and to consciousness with great skill and thoroughness, making it an important reference point within the literature. As it happens, I am firmly opposed to the author’s position, but I shall try here both to set out the author’s case, which is very strong, as well as my own disagreement.

The argument of the book proceeds through three stages. First, a critique is provided of the reasoning that has led many authors, from Descartes onwards, to adopt some form of dualistic approach. Next follows a critique of the arguments suggesting that quantum theory implies a role for a dualistic consciousness, or at least introduces an important indeterminism into the universe. Finally, a compatibilist account is given of how human decision making and ethics can properly be justified on the basis of mechanistic determinism. A number of other pertinent issues, such as the flow and directionality of time, are interestingly dealt with en route.

The first of these stages, countering dualism, is the main foundation of the book, and the pivotal point of this stage is an enquiry into the nature of consciousness in Chapter 2. First, we have a good critical review of those who regard consciousness as extra-physical. But then we encounter the Great Divide in consciousness research. Drescher stands on one side with Dennett and many others who propose some particular structural feature that distinguishes conscious thought from unconscious mental processes. On the other side stand Chalmers, Velmans and those who argue that consciousness is more than this, on the grounds that any particular structure of mental processing could always be conceived of as occurring without consciousness (but without thereby proposing what Drescher dismissively calls “ghosts”). To understand the difference between the two sides, consider Drescher’s statement: “Of course there is something we perceive when we think we perceive our extra-physical consciousness - that is, when we perceive conscious events such as our thoughts, feelings, perceptions , and so on.” It is clear from this that for him consciousness is something we perceive, or an aspect of things we perceive. For Velmans, however, “consciousness” is essentially synonymous with “awareness”, and is not what we perceive but that whereby we perceive. It is not a matter just of different theories, but of using the same word for two different things. Drescher does not refer to consciousness in Velmans’ sense. I would speculate that he would not recognise its existence, perhaps through not having training in the appropriate introspective tools for examining it, a lack that becomes crucial later in the book.

Drescher does, however, talk a great deal of sense about “consciousness” as he defines it, a structural aspect that is indeed present as part of everyday conscious awareness. In particular, he gives a succinct account (following Dennett) of the inadequacy of the “Cartesian Theatre” image of consciousness, in which percepts are, as it were, projected on an internal screen, where everything comes together, to be viewed by some internal self (whose operation is then as mysterious as the original human). He then offers a convincing alternative metaphor of the “Cartesian camcorder” in which perception is played back, after a short or long delay, so that it can at this stage be processed, related to the self-image and so on. It would be fascinating to investigate the way this picture could be expanded by detailed experimental research in cognitive psychology, such as that by members of Phil Barnard’s group in Cambridge, who find evidence for two “camcorders” of this form, with consciousness switching between them.

Stage 2 of the argument for mechanism analyses quantum theory with a view to showing that both the idea of observer-dependence, and the idea of the collapse of the state, are unnecessary metaphysical additions to a deterministic quantum formalism. As with the previous stage, there are some well presented arguments, and demystifications of entrenched views, but also some crucial omissions. He gives a careful account of Everett’s relative state approach, using a “toy” version of quantum theory which illustrates the essential features, but which is accessible to the (enthusiastic) reader unfamiliar with quantum formalism. On this approach there are multiple copies of organisms such as our ourselves, branching when we interact with quantum systems in particular ways, but there is no need to complicate the picture with a metaphysics of “many worlds”, as is often done on this approach. The presentation thus parallels the “many minds” approach of Butterfield and others.

The problem with this, however, is that in real quantum theory the whole picture is dependent on a particular choice of basis in the Hilbert space of quantum mechanics at each instant of time, unlike his toy theory where such a choice is fixed from the start by the assumptions. The work of Dowker and Kent (from which the work of Kent cited by Drescher diverged) shows that there always exist alternative choices to the “correct” one that also satisfy Everett’s criteria for a “good observation” but which correspond to absurd universes. While Drescher correctly criticises the Copenhagen interpretation for having “no formal criterion for what constitutes an observation”, he ignores the equivalent problem that the Everett interpretation has no formal criterion for what is an acceptable basis of the Hilbert space of states. The same problem persists into the various versions of the histories interpretation (such as Hartle’s “generalised quantum theory”) which are the successors to Everett’s theory. Proposals here for a choice of basis, such as Zeh’s pointer basis, are too informal for general use. In other words, all the interpretations of quantum theory, including Everett’s, are incomplete.

It is this lacuna in Everett’s approach (and in the more developed modern histories approach) that calls out for an extension of orthodox quantum theory by a non-deterministic element, or by consciousness, or both. The first is exemplified by Penrose’s recent work (which Penrose formulates it in terms of a “collapse” metaphysics, though this is not strictly necessary). Drescher skilfully critiques the part of this dealing with Gödel’s theorem, but he ignores the application of Penrose’s work to the basis problem. Penrose also introduces the idea of consciousness as playing a part here, but it is Stapp who shows how consciousness, in Velmans’ sense rather than Drescher’s, can effectively fill this lacuna - without falling foul of the problem of multiple causation which arises in the Cartesian approach. Thus Drescher fails to address the main argument for an active, non-deterministic role of consciousness in the universe.

While the first two stages suffered from crucial omissions, it was the third stage in the argument, with the treatment of ethics at its core, that I found the most problematic. Here we move from interesting speculations about physics to matters of the survival of human civilisation. At the start there is again much excellent work of clarification: the early chapters of this stage constitute the most convincing defence that I have read of the compatibilist position, that determinism is compatible with free choice. Moving on from this, Drescher addresses the issue of ethics, which he rightly treats as vital to our human condition. He asserts that “the post-modern retreat from objectivity ... is disastrous with regard to ethics” and on the basis of this sets out to construct “objective” foundations for ethics. First, he identifies “post-modernism” with “ethical relativism”, and therewith dismisses most of modern ethical thinking in favour of such minimal ethics as can be derived from a purely rationalist, utilitarian (in the broad sense) approach.

The problem here is a confusion between relativity and relativism. Einstein’s general relativity, as an example, analyses the relativity of the perspectives of different observers in order to construct a new absolute: curved space time. Similarly, post-modernism discloses the relativity caused by conditioning by society in order (in the hands of the eminences of post-modernism such as Derida and Lacan) to find a new absolute for human ethics – though many fail to take that step and turn relativity into relativism. This new absolute lies not in the “objective” (in the sense of a structure independent of consciousness) but in those aspects of the subjective that go beyond the individual. The “objective” ethic praised by Drescher depends on an assignment of relative values to goals that is necessarily dependent on society, and is hence subject to the manipulation of values by commercial interests. Within postmodernism, on the other hand, it has been argued (notably by Jennifer Crawford) that an absolute is attainable in the subjectivity that is part of human physiology, and thus universal, as opposed to human culture which is realtive. There is an urgent need for a more informed debate here, of which Drescher presents one side with great clarity.

To return to the positive: the clarity of this book clears the ground of many myths that hold us back. I advice readers to buy it, read it and then build upon it.