The Mechanical Mind

A Philosophical Introduction to Minds, Machines and Mental Representation

Tim Crane

• Publisher: Routledge
• Year: 2015
• ISBN:
  9781317331780
• Edition: 3
• Topic: Filosofía
• Subtopic: Historia y teoría filosóficas

How can the human mind represent the external world? What is thought, and can it be studied scientifically? Should we think of the mind as a kind of machine? Is the mind a computer? Can a computer think? Tim Crane sets out to answer these questions and more in a lively and straightforward way, presuming no prior knowledge of philosophy or related disciplines.

Since its first publication, The Mechanical Mind has introduced thousands of people to some of the most important ideas in contemporary philosophy of mind. Crane explains the fundamental ideas that cut across philosophy of mind, artificial intelligence and cognitive science: what the mind–body problem is; what a computer is and how it works; what thoughts are and how computers and minds might have them. He examines different theories of the mind from dualist to eliminativist, and questions whether there can be thought without language and whether the mind is subject to the same causal laws as natural phenomena. The result is a fascinating exploration of the theories and arguments surrounding the notions of thought and representation.

This third edition has been fully revised and updated, and includes a wholly new chapter on externalism about mental content and the extended and embodied mind. There is a stronger emphasis on the environmental and bodily context in which thought occurs. Many chapters have been reorganised to make the reader's passage through the book easier. The book now contains a much more detailed guide to further reading, and the chronology and the glossary of technical terms have also been updated.

The Mechanical Mind is accessible to anyone interested in the mechanisms of our minds, and essential reading for those studying philosophy of mind, philosophy of psychology, or cognitive psychology.

1
Introducing the mechanical mind

1.1 The mechanical world picture

This book is about the philosophical problem of mental representation. How can the mind represent anything? How can thoughts, experiences, desires, intentions and all the other mental states come to represent other things? My belief, for example, that President Nixon visited China is about Nixon and China – but how can a state of my mind be ‘about’ Nixon or China? How can my state of mind direct itself on Nixon and China? What is it for a mind to represent anything at all? For that matter, what is it for anything (whether a mind or not) to represent anything else?

This problem, which some contemporary philosophers call ‘the problem of intentionality’, has ancient origins. But developments in philosophy of mind – together with developments in the related disciplines of linguistics, psychology and artificial intelligence – have raised the old problem in a new way. So, for instance, the question of whether a computer could think is closely tied up with the problem of intentionality. And the same is true of the question of whether there can be a ‘science of thought’: can the mind be explained by science, or does it need its own distinctive, non-scientific mode of explanation? A complete answer to this question depends, as I will explain, on the nature of mental representation.

Underlying most recent attempts to answer questions like these is what I am calling the ‘mechanical’ view of the mind, or ‘the mechanical mind’ for short. This is the view that the mind is a causal mechanism, a natural part of natural organisms which functions in a systematic, regular way. The mind is a kind of natural machine or mechanism. Representation is considered a problem because it is hard to understand how a mere mechanism or machine can represent the world – how states of the mechanism can ‘reach outside’ and direct themselves upon the world. This first chapter will give more of an idea of what I mean when I talk about the mechanical mind, by outlining the origins of the idea.

The idea that the mind is a natural mechanism derives from thinking of nature itself as a kind of mechanism. So to understand this way of looking at the mind we need to understand – in very general terms – this way of looking at nature.

The modern Western view of the world traces back to the ‘Scientific Revolution’ of the seventeenth century, and the ideas of Galileo, Francis Bacon, Descartes and Newton. In the Middle Ages and the Renaissance, the world had been thought of in organic terms. The earth itself was thought of as a kind of organism, as this passage from Leonardo da Vinci colourfully illustrates:

We can say that the earth has a vegetative soul, and that its flesh is the land, its bones are the structures of the rocks … its blood is the pools of water … its breathing and its pulses are the ebb and flow of the sea.¹

This organic world picture, as we could call it, owed a vast amount to the works of Aristotle, the philosopher who had by far the greatest influence over the thought of the Middle Ages and the Renaissance. (In fact, his influence was so great that he was often just called ‘the Philosopher’.) In Aristotle’s system of the world, everything had its natural ‘place’ or condition, and things did what they did because it was in their nature to achieve their natural condition. This applied to inorganic things as much as to organic things – stones fall to the ground because their natural place is to be on the ground, fire rises to its natural place in the heavens, and so on. Everything in the universe was seen as having its final end or goal, a view that was wholly in harmony with a conception of a universe whose ultimate driving force is God.

In the seventeenth century, this all began to fall apart. One important change was that the Aristotelian method of explanation – in terms of final ends and ‘natures’ – was replaced by a mechanical or mechanistic method of explanation – in terms of the regular, deterministic behaviour of matter in motion. And the way of finding out about the world was not by studying and interpreting the works of Aristotle, but by observation and experiment, and the precise mathematical measurement of quantities and interactions in nature. The use of mathematical measurement in the scientific understanding of the world was one of the key elements of the new ‘mechanical world picture’. Galileo famously spoke about:

This grand book the universe, which … cannot be understood unless one first comes to comprehend the language and to read the alphabet in which it is composed. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures, without which it is humanly impossible to understand a single word of it.²

The idea that the behaviour of the world could be measured and understood in terms of precise mathematical equations, or laws of nature, was at the heart of the development of the science of physics as we know it today. To put it very roughly, we can say that, according to the mechanical world picture, things do what they do not because they are trying to reach their natural place or final end, or because they are obeying the will of God, but, rather, because they are caused to move in certain ways in accordance with the laws of nature.

In the most general terms, this is what I mean by a mechanical view of nature. Of course, the term ‘mechanical’ was – and sometimes still is – taken to mean something much more specific. Mechanical systems were taken to be systems which interacted only on contact and deterministically, for instance. Later developments in science – e.g. Newton’s physics, with its postulation of gravitational forces which apparently act at a distance, or the discovery that fundamental physical processes are not deterministic – refuted the mechanical world picture in this specific sense. But these discoveries do not, of course, undermine the general picture of a world of causes which works according to natural laws or regularities; and this more general idea is what I mean by ‘mechanical’ in this book.

In the ‘organic’ world picture of the Middle Ages and the Renaissance, inorganic things were conceived along the lines of organic things. Everything had its natural place, fitting into the harmonious working of the ‘animal’ that is the world. But with the mechanical world picture, the situation was reversed: organic things were thought of along the lines of inorganic things. Everything, organic and inorganic, did what it did because it was caused by something else, in accordance with principles that could be precisely, mathematically formulated. René Descartes (1596–1650) was famous for holding that non-human animals are machines, lacking any consciousness or mentality: he thought that the behaviour of animals could be explained entirely mechanically. And as the mechanical world picture developed, the watch, rather than the animal, became a dominant metaphor. As Julien de La Mettrie, an eighteenth-century pioneer of the mechanical view of the mind, wrote: ‘the body is but a watch … man is but a collection of springs which wind each other up.’³

So it is not surprising that, until the middle of this century, one great mystery for the mechanical world picture was the nature of life itself. It was assumed by many that there was in principle a mechanical explanation of life to be found – Thomas Hobbes had confidently asserted in 1651 that ‘life is but a motion of limbs’⁴ – the only problem was finding it.

Gradually, more and more was discovered about how life was a purely mechanical process, culminating in the discovery of the structure of DNA by Watson and Crick in 1953. Now, it seems, the ability of organisms to reproduce themselves can be explained, in principle, in chemical terms. The organic can be explained in terms of the inorganic.

1.2 The mechanical world picture and the human mind

Where did this leave the mind? Though he was perfectly willing to regard animals as mere machines, Descartes did not do the same for the human mind: although he did think that the mind (or soul) has effects in the physical world, he placed it outside the mechanical universe of matter. But many mechanistic philosophers in later centuries could not accept this particular view of Descartes’s, and so they faced their biggest challenge in accounting for the place of the mind in nature. The one remaining mystery for the mechanical world picture was the explanation of the mind in mechanical terms.

As with the mechanical explanation of life, it was assumed that of course there was going to be such an explanation of the mind. Good examples of this assumption can be found in the slogans of eighteenth- and nineteenth-century materialists: La Mettrie’s remark that ‘the brain has muscles for thinking as the legs have muscles for walking’, or the physiologist Karl Vogt’s slogan that ‘the brain secretes thought just as the liver secretes bile’.⁵ But these are just materialist rallying cries rather than substantial theories.

So what would a mechanical explanation of the mind be like? One influential idea in the philosophy of the last forty years is that to explain the mind would involve showing that it is really just matter. Mental states really are just chemical states of the brain. This materialist (or ‘physicalist’) view normally depends on the assumption that to explain something fully is ultimately to explain it in terms of physical science. In other words, sciences other than physics must have their scientific credentials vindicated by physics – all sciences must be reducible to physics. Standardly, what this means is that the contents of sciences other than physics must be deducible or derivable from physics (plus ‘bridge’ principles linking physical concepts to non-physical concepts) and that, therefore, everything that is explicable by any science is explicable in terms of physics. This is the view – sometimes known as ‘reductionism’ – which lies behind Rutherford’s memorable quip that ‘there is physics; and there is stamp-collecting’.⁶

This extreme reductionism is really very implausible, and it is very doubtful whether scientific practice actually conforms to it. Very few non-physical sciences have actually been reduced to physics in this sense, and there seems little prospect that science in the future will aim to reduce all sciences to physics. If anything, science seems to be becoming more diversified rather than more unified. For this reason (and others) I think we can distinguish between the general idea that the mind can be mechanically explained (or causally explained in terms of some science or other) and the more extreme reductionist thesis. One could believe that there can be a science of the mind without believing that this science has to reduce to physics. I will return to reductionism and physicalism at a number of places in this book (Chapters 4 and 12). But it should be noted right away that the most reasonable version of physicalism does not entail that all sciences reduce to physics in the sense just described. A more reasonable version of physicalism holds only that all the facts are fixed by the fundamental physical facts. A useful image is this: imagine God creating the world, and ask yourself, what would God have to do to create this world, just as it is? Physicalism says that all God would have to do would be to create the world’s underlying physical nature. Everything else would come into existence ‘for free’, since it is determined or fixed by the physical nature of the world. The philosophical term for this doctrine is ‘supervenience’: everything ‘supervenes’ on the physical. This does not imply anything about whether everything can be explained by physics.

This book is not about physicalism. A lot of what I say here is compatible with physicalism, but physicalism as such does not directly answer the questions I am trying to answer here. That is because I am interested in understanding how the mind – and in particular mental representation – can be explained. Merely saying that the mental, like everything else, supervenes on the physical does not explain how the mind works. What I am calling a ‘mechanical’ explanation of the mind must explain how the mind is part of the world of causes and effects – part of what philosophers call the ‘causal order’ or the world. Another thing which such an explanation of the mind must do is articulate the generalisations which describe causal regularities in the mind. In other words, a mechanical explanation of the mind is committed to the existence of something like natural laws of psychology. Just as physics finds out about the laws which govern the non-mental world, so psychology finds out about the laws which govern the mind: on the mechanical picture, there can be a natural science of the mind.

Yet while this view is embraced in its broad outlines by many philosophers of mind, the details of its application to the phenomena of mind are deeply problematic. Two kinds of phenomenon stand out as obstacles to the mechanical view of mind: the phenomenon of consciousness and the phenomenon of thought. Hence, recent philosophy of mind’s preoccupation with two questions: first, how can a mere mechanism be conscious? And second, how can a mere mechanism think about and represent things? The central theme of this book is the one generated by the second question: the problem of thought (called ‘intentionality’) and mental representation. Most of the book is concerned with this problem. But a full treatment of the mechanical mind also needs to say something about the problem of consciousness: no mechanical theory of the mind which failed to address this most fundamental mental phenomenon could be regarded as a complete theory of the mind. In the final chapter, I will address this question. However, as will become obvious as the book goes on, I do not think the phenomena of consciousness and intentionality can be neatly separated. It follows that a lot of what is said about intentionality will carry over to the discussions of consciousness.

1.3 Prospectus

The thirteen chapters of this book are designed to be read in succession, though some material can be skipped where indicated. We start with the general problem of representation (Chapter 2) and then move on to discuss mental representation in Chapter 3. This leads to the question of how we understand the mind from the common-sense, non-scientific point of view (Chapter 4) and from the scientific point of view (Chapter 5). The bas...