This book is an attack by an "insider" on the contemporary disciplines of cognitive science and evolutionary psychology.
Fodor does not deny that there are some valid aspects to these two disciplines. Rather, he rejects their extravagant claims to have successfully explained "The Way the Mind Works," to quote the title of a recent book by Steve Pinker, who is one of the leading evangelists for cognitive psychology and evolutionary psych.
Fodor's central complaint against evolutionary psychology is quite simple. Anyone who claims to offer an evolutionary explanation for the wings of birds can start with a great deal of solid knowledge about how bird's wings are in fact constructed, about how wings make flight possible given the laws of aerodynamics, etc.
But no one in fact yet possesses the equivalent information for the brain and the mind.
We do not yet know how the neurons are connected and in what manner they function so as to produce thought. More basically, we do not understand what "mind" really is from the viewpoint of the underlying physics of the brain (see, e.g., David Chalmers' "The Conscious Mind" or Colin McGinn's "The Mysterious Flame").
Fodor also has more specific objections. He is highly concerned with the issue of "abduction," the ability to make global judgments of simplicity, relevance, etc. over a broad intellectual domain. Fodor believes that humans are very good at this, but that the current "modular" approach pursued by cognitive scientists and evolutionary psychologists cannot explain how humans could be good at this.
I'm not sure human judgment is as powerful as Fodor believes, but he is correct that modular systems have difficulty making broad global judgments.
In his final chapter, Fodor directly addresses the issue of evolution, arguing that, for a feature to be the product of natural selection, it must be built up by a small number of steps. Using the example of the giraffe's neck, he argues, "Make the giraffe's neck just a little longer and you correspondingly increase, by just a little, the animal's ability to reach the fruit at the top of the tree; so it's plausible, to that extent, that selction stretched giraffe's necks bit by bit."
This example is somewhat misleading: there is no reason in principle why a single mutation could not have created huge giraffe necks in one fell swoop and natural selection then stepped in to preserve the mutation.
But Fodor is correct that such a "saltationist" explanation is not available to evolutionary psychology. The plethora of specialized mental modules favored by evolutionary psychologists (a language module, a "cheater detection module," a face-recognition module, a theory-of-mind module, to name only a few) are supposed to be carefully honed adaptations exquisitely polished by natural selection to serve human needs in the "ancestral environment" (the Paleolithic). Just as a complex organ such as the eye could not realistically be created in one single fortuitous mutation, so neither could these complex mental "organs" hypothesized by evolutionary psych.
But why does Fodor reject a gradual, multifaceted evolution of these hypothetical mental "organs"? He does not say, but there is a fairly powerful argument from the human genome project. We only have about 30,000 genes; most of these are shared with lower mammals and many with non-vertebrates and even non-animals. There just are not that many genes left which distinguish us from mice.
A change in a relatively small number of regulatory genes can bring dramatic changes in development -- our much larger brain, for example. But to actually create a number of new specialized "organs," not possessed by mice or cows places much greater demands on the genome. It's doubtful we have enough genes to handle it.
The evolutionary psych response, as made in Pinker's "The Blank Slate," to this argument is in essence that since these mental modules _do_ exist, our genes _must_ be able to produce the modules. That of course assumes what is to be proven, i.e., that the human mind is based on evolutionarily-derived specialized mental modules.
Fodor completely demolishes the claim that the unity of science demands that evolutionary psychology be true. The degree to which the science of evolution is relevant to the science of psychology is, he rightly argues, an empirical matter, just as (to use his example) it is an empirical matter whether "the theory of lunar geography constrains the theory of cellular mitosis." Not every science has to be relevant to every other science.
Fodor also shreds what he calls "neo-Darwinist anti-intellectualism," the view (he is quoting from Patricia Churchland) that "looked at from an evolutionary point of view, the principal function of nervous systems is to get the body parts where they should be in order that the organism may survive...Truth, whatever that is, definitely takes the hindmost."
Fodor counters that for humans "a cognitive system that is specialized for the fixation of true beliefs interacts with a conative system that is specialized to figure out how to get what one wants from the world that the beliefs are true of..." or, in simple English, humans engage in "rational actions predicated on true beliefs."
We are designed to pursue both truth and our own well-being -- there is no contradiction here. Not action instead of truth, but action based on truth.
Despite the brief length and Fodor's engaging style, this book is not easy reading. But it does raise questions which, if not adequately answered by Fodor's opponents, cast grave doubts on the grandiose claims of contemporary apostles of cognitive science and evolutionary psychology.