Since the 17th century the march of science has swept all before it. The route mapped out by Copernicus, Newton, Darwin and Einstein is dotted with numerous significant milestones along the way, giving hope that in time even the remotest regions of the universe and the innermost secrets of the atom will be exposed by science. Or will they? For there is one thing—at once the most obvious and most mysterious thing of all—that has so far resisted the best efforts of scientist and philosopher alike: the human mind.
We are all immediately conscious of our consciousness—that we have thoughts, feelings, desires that are subjective and private to us; that we are actors at the center of our world and have a unique and personal perspective on it. In stark contrast, science is triumphantly objective, open to scrutiny, eschewing the personal and the perspectival. So how can something as strange as consciousness conceivably exist in the physical world that is being exposed by science? How are mental phenomena explicable in terms of, or otherwise related to, physical states and events in the body? These questions together form the mind-body problem, arguably the thorniest of all philosophical issues.
As in epistemology (the philosophy of knowledge), so in the philosophy of mind, the Frenchman René Descartes made an impact in the 17th century that has reverberated through Western philosophy till the present day. Descartes’s refuge in the certainty of his own self (see Cogito ergo sum) naturally led him to give an exalted status to mind in relation to everything in the world outside it. In metaphysical terms, he conceived mind as an entirely distinct entity—as mental substance, whose essential nature is thinking. Everything else is matter, or material substance, whose defining characteristic is spatial extension (i.e. filling physical space). Thus he envisaged two distinct realms, one of immaterial minds, with mental properties such as thinking and feeling; another of material bodies, with physical properties such as mass and shape. It was this picture of the relation between mind and matter, known as “substance dualism,” that Gilbert Ryle pilloried as the “dogma of the Ghost in the Machine.”
In his book The Concept of Mind (1949) the English philosopher Gilbert Ryle argues that Descartes’s dualist conception of mind and matter is based on a “category mistake.” Imagine, for instance, a tourist who is shown all the separate colleges, libraries and other buildings that make up Oxford University, and then complains at the end of the tour that he hasn’t seen the university. The tourist has wrongly ascribed both the university and the buildings of which it is composed to the same category of existence, thus entirely misrepresenting the relation between the two. In Ryle’s view, Descartes has made a similar blunder in the case of mind and matter, mistakenly supposing them to be completely different substances. From this dualist metaphysics arises Ryle’s disparaging picture of the “Ghost in the Machine”: the immaterial mind or soul (the Ghost) somehow living within and pulling the levers of the material body (the Machine). After delivering his withering attack on Cartesian dualism, Ryle goes on to present his own solution to the mind-body problem—behaviorism (see The Turing test).
“The dogma of the Ghost in the Machine … maintains that there exist both bodies and minds; that there occur physical processes and mental processes; that there are mechanical causes of corporeal movements and mental causes of corporeal movements.”
Gilbert Ryle, 1949
Problems for dualism A desire to drink causes my arm to lift the glass; a drawing pin in my foot causes me pain. Mind and body (so common sense suggests) interact: mental events bring about physical ones, and vice versa. But the need for such interaction immediately casts doubt on the Cartesian picture. It is a basic scientific principle that a physical effect requires a physical cause, but by making mind and matter essentially different, Descartes appears to have made interaction impossible.
Descartes himself recognized the problem and realized that it would take God’s intervention to effect the necessary causal relationship, but he did little else to resolve the issue. Descartes’s younger contemporary and follower, Nicolas Malebranche, accepted his dualism and took it upon himself to grapple with the causation problem. His surprising solution was to claim that interaction did not in fact occur at all. Instead, on every occasion when a conjunction of mental and physical events was required, God acted to make it happen, so creating the appearance of cause and effect. The awkwardness of this doctrine, known as “occasionalism,” has won little support and serves principally to highlight the seriousness of the problem it was intended to fix.
A tempting way to avoid some problems facing the Cartesian position is property dualism, originating in the work of Descartes’s Dutch contemporary, Baruch Spinoza, who claims the notion of dualism relates not to substances but to properties: two distinct types of property, mental and physical, can be ascribed to a single thing (a person or subject), but these attributes are irreducibly different and cannot be analyzed in terms of one another. So the different properties describe different aspects of the same entity (hence the view is sometimes called the “double aspect theory”). The theory can explain how mind-body interaction occurs, as the causes of our actions themselves have both physical and mental aspects. But, in ascribing such essentially different properties to a single subject, there is a suspicion that property dualism has merely shifted the most daunting problem facing substance dualism, rather than solving it.
Descartes may have made the classic statement of substance dualism, but he was by no means the first. Indeed, some form of dualism is implicit in any philosophy, religion or world-view that presupposes there is a supernatural realm in which immaterial bodies (souls, gods, demons, angels and the like) reside. The idea that a soul can survive the death of a physical body or be reincarnated in another body (human or other) also requires some kind of dualist conception of the world.
Physicalism The obvious response to the difficulties facing the substance dualism of Descartes is to adopt a monistic approach—to claim that there is only one kind of “stuff” in the world, either mental or physical, not two. A few, most notably George Berkeley (see The veil of perception), have taken the idealist path, claiming that reality consists of nothing but minds and their ideas, but the great majority, certainly amongst today’s philosophers, have opted for some form of physicalist explanation. Driven on by the undeniable successes of science in other areas, the physicalist insists that the mind, too, must be brought within the purview of science; and since the subject matter of science is exclusively physical, the mind must also be physical. The task then becomes to explain how mind (subjective and private) fits into a complete and purely physical account of the world (objective and publicly accessible).
Physicalism has taken a number of different forms, but what these have in common is that they are reductive: they claim to show that mental phenomena can be analyzed, fully and exhaustively, in purely physical terms. Advances in neuroscience have left little doubt that mental states are intimately related to states of the brain. The simplest course for the physicalist is thus to claim that mental phenomena are actually identical to physical events and processes in the brain. The most radical versions of such identity theories are “eliminative”: they propose that, as our scientific understanding advances, “folk psychology”—our ordinary ways of thinking and expressing our mental lives, in terms of beliefs, desires, intentions and so on—will disappear, to be replaced by accurate concepts and descriptions drawn principally from neuroscience.
Physicalist solutions to the mind-body problem brush aside many of the difficulties of dualism at a stroke. In particular, the mysteries of causation that torment dualists are dispelled by simply bringing consciousness within the scope of scientific explanation. Predictably, critics of physicalism complain that its proponents have brushed aside too much; that its successes have been achieved at the heaviest cost—of failing to capture the essence of conscious experience, its subjective nature.
the condensed idea
Mind boggles
| Timeline | |
|---|---|
| 1637 | The mind-body problem |
| 1644 | Cogito ergo sum |
| 1665 | The ship of Theseus |
| 1690 | The veil of perception |
| 1912 | Other minds |
| 1950 | The Turing test |
| 1974 | What is it like to be a bat? |