Minds, for the use of

Philosophers' attempts to grapple with the mind have largely focused on answering questions about what minds are. Peter Godfrey-Smith's book is a welcome attempt to take a long philosophical look at the question of why minds exist at all. Evolutionary biologists (unlike almost all other disciplines in science) have long regarded "why?" questions of this kind as being of great importance.

"Why?" questions are important in that they broach the most fundamental questions of existence. With the possible exception of cosmologists, scientists have generally eschewed such issues, mostly in the mistaken belief that to ask them commits us to metaphysics or worse. But in biology, "why?" questions are at the very heart of the evolutionary process. To be sure, the answer must always be one of adaptive purposiveness and not the kind of teleological response so characteristic of the philosophical past. To distinguish them clearly from the latter kind of nonsense, the biological (or evolutionary) approach is sometimes said to be teleonomic - that is to say, it focuses on the mechanisms that drive the system in one direction rather than another. The thermostat is a teleonomic device in this sense. In the biological context, the mechanism is natural selection.

Godfrey-Smith's claim is that the mind evolved as a response to the need to deal with environmental complexity. "A central project in philosophy of mind over the last few decades," he observes, "has been the attempt to give a naturalistic analysis of intentionality, the attempt to say I what it is for an internal state of a system like a brain to represent or be about some other object or state of affairs". His aim, in contrast, is to show "that a basic mental tool kit has the function of enabling agents to deal with environmental complexity: that is, why the tool kit is there." His thesis, as he points out, does not depend on any particular theory as to how this cognitive machinery actually works; indeed, it is compatible with a number of theories of how thought manages to perform its everyday tasks.

Godfrey-Smith conceives his task in two parts. The first part of the book is a lengthy analysis of the positions of two once-influential philosophers, the Victorian Englishman Herbert Spencer and the latter-day American John Dewey. Godfrey-Smith intends these two to provide him with foils for exploring an externalist theory of the mind without need to commit himself to espousing either of their views in any detail.

He argues that, in their different ways, Spencer and Dewey provide complementary standpoints. Spencer's evolutionism led him to place a central emphasis on the mind as mechanism for coordinating behaviour (itself seen as the body's response to environmental complexity). Spencer is, in many ways, the point of intersection between the two most important streams in the 19th-century British intellectual scene, namely the empiricist philosophical tradition of Locke and Hume and the new evolutionary theories of the biologists. Dewey, doyen of the turn-of-century pragmatists, viewed beliefs as instrumental guides to action. Both focused on the role that thought plays in enabling the body to respond to a complex and variable environment.

In his attempt to develop a coherent externalist theory of the mind, Godfrey-Smith is uncompromising in his dismissal of the sillier features of the alternative internalist (or constructivist) theories. These relativist views are apt to see the external world as a mere construction of the way we are socialised to use language. Biologists in particular have always found the narcissism inherent in the constructivist view frankly offensive.

Godfrey-Smith's aim, then, is not to provide a theory of the location of the mental in the physical (the mind-qua-brain stories we associate with much conventional philosophy of mind) but rather to elucidate the role of the mind in nature and what we use it for.

In the second half of the book, he tries to get to grips with this question with the aid of some mathematical models. Drawing on the biological concept of fitness maximisation, he attempts to show that the ability to manipulate the world mentally in order to be able to predict optimal responses to environmental vagaries would be selectively advantageous. He sees the processes involved as analogous to a Bayesian model of experimentation. Indeed, his whole argument hinges around the question of when it would pay an organism to evolve the (rather expensive) capacity to learn.

These models are mainly game-theory models of the kind that are commonly used in evolutionary biology to assess selection advantages when an organism has a choice of alternative ways to proceed. Since decisions of this kind depend on mechanisms for acquiring information about the environment, Godfrey-Smith supplements his analysis with models derived from signal detection theory.

This has been a long-overdue exercise, and one that will strike a chord with evolutionary biologists. My own quibbles with the book rest on the fact that he devotes far too little attention to the so-called "social brain" hypothesis - the increasingly influential view that brain (and hence mind) evolution within the primates owes its origins not to the need to handle environmental complexity but to the growing need to handle the infinitely more complex problems of the social world. It is not an exaggeration to say that the average human mind daily executes calculations in the social domain of an order of complexity not far off that required to understand quantum theory. Yet most of us wilt at the mere sight of even a simple Newtonian physics equation.

In the end, the success of this book will obviously depend on how well it can convince not biologists but psychologists and philosophers. I fear that many of them will find the second half of this book difficult to follow. That will be a pity but in the interests of genuine interdisciplinary exchange I can only encourage them to persevere.

Robin Dunbar is professor of psychology, University of Liverpool.