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Dualism: An Introductory Exploration (2001)
Brenton Priestley

"It is not that I think I can give a knock-down proof that dualism, in all its forms, is false or incoherent, but that, given the way dualism wallows in mystery, accepting dualism is giving up" (Dennett, Consciousness Explained, p.37). What is dualism? What forms does it take? Why does Dennett think that "accepting dualism is giving up"? Is he right? Defend your answer."



Introduction to Dualism

Throughout history, it has seemed obvious that humans possess something that no other living organisms do, something that has allowed us to experience things ranging from justice to mathematics, from music to melancholy. This awareness of things that cannot be physically defined has, naturally enough, lead to the long-standing idea that humans possess a mind, capable of conscious thought and rationalisation, that is quite separate from the physical world around us. It was Ren´┐Ż Descartes that proposed the first significant description of the nature of the mind. His idea, that mind and brain are two separate entities, is known as Cartesian dualism. Several other dualist theories also exist.

In recent years, however, dualism has faltered in the face of scientific developments in neuropsychology and evolutionary theory. The majority of scientists and philosophers now reject a dualist theory of mind. Materialism, the theory that everything in the universe is composed of physical matter that can be systematically studied through scientific methods, is more popular.

Although the case against dualism seems to be a strong one, it is important to analyse the merits of various forms of dualist theories. The significance of the mind-brain debate is perhaps expressed best in Warner’s comment that ‘...it is difficult to imagine a philosophical issue more fundamental to our understanding of science and self’ (Warner 1994 p.13).

Forms of Dualism

Of all the forms that dualism has taken, it is the Cartesian view, also known as substance dualism, that remains widespread and the most persuasive. However, the problem of interaction (which will be discussed later) inherent in substance dualism, has lead to the development of other dualist theories, all of which are nonetheless far more explanatorily impotent. The most common form of non-interactionist dualism is Property Dualism. Two other fairly minor forms, Occasionalism and Parallelism illustrate the tenuous position of Dualism and the extent to which proponents attempt to justify it.

    1. Substance Dualism
    2. According to substance dualism, the mind is a completely separate entity from the brain. It is composed of a non-physical substance that, unlike normal physical matter, has no extension in space. Physical experience is transferred from the physical brain to the mind. The function of the mind is conscious, rational thought. The defining part of a person is thus this mind, and when their physical body dies, the mind (or soul, as it is known in religious contexts) will live on.

    3. Property Dualism
    4. Physical substances can differ in their properties, but still be composed of the same substances; for instance, water can be frozen or boiling. Property dualism postulates that what we perceive to be the mind is a variety of mental properties of the physical brain. A version of property dualism, epiphenomenalism, states that physical, bodily events give rise to mental events, but mental events cannot cause physical ones; the physical brain controls such events.

    5. Psychophysical Parallelism and Occasionalism

The parallelist form of dualism states that mind and body exist separately, but do not actually interact with one another. God, or ‘...a quite staggering cosmological coincidence’ (Warburton 1995 p.130) has set both mind and brain in parallel to one another, causing them to appear to interact.

Occasionalism is similarly implausible; according to the theory, God provides the link between mind and brain. When a person’s mind decides to kick a ball, it is God that then moves their leg and foot towards the ball.

The last three forms of dualism are inherently flawed and few dualists advocate them. Thus, the remainder of this paper will focus on substance dualism; arguments for and against it, and a response to Dennett’s claim that accepting dualism is ‘giving up’ (p.37).

Arguments for Dualism

To each person who experiences the world around them, a dualist view of mind and brain seems to make logical sense. How could feelings of love, or an appreciation of art rise from a purely physical system? It is for this reason that dualism has been such a common and plausible view for so long. This, also known as the argument from introspection, is the first of the several arguments for dualism outlined by Churchland (1988 p.13).

The second, the argument from religion, acknowledges that a fundamental aspect of the world’s major religions is that humans have a soul that is separate from the body. To deny this dualism is to ultimately deny the beliefs of billions of people.

Descartes questioned whether reasoning and language are possible in a totally physical universe (Quoted in ibid. p.14). Similarly, the nature of thoughts, beliefs and sensations (also known as sensory qualia) seem to similarly defy physical explanation. This is known as the argument from irreducibility.

Descartes ultimately concluded that the mind and brain were separate through a series of logical steps in his Meditations on First Philosophy. His idea, ‘I think, therefore I am’ sprung from the conclusion that his only belief that was not in doubt was that he existed as a conscious, thinking being. Therefore, if he could conceivably exist without a body, then the mind must be independent (Quoted in Bechtel 1988 p. 81).

The most appealing thing about dualism is that it gives a special status to human beings. Without a mind separate from the body, the logical materialist view would state that there is no free will, and nor can a human be worth any more than any other physical matter. ‘A dualist perspective,’ writes Bechtel, ‘[is] essential to our understanding of the moral and religious status of human beings.’ (Ibid. p.86)

Unfortunately, though, from a scientific standpoint, the outlook for dualism is bleak.

Arguments against Dualism

O’Brien outlines three major problems with dualism (O’Brien 2001 p.4). Firstly, if the mind is separate from the body, then why are all minds associated with the bodies and brains of those who possess them? Secondly, if bacteria don’t have minds, but humans do, how is it possible for this non-physical substance to have evolved from a physical one? Thirdly, and most significantly is the problem of causal efficacy, or interaction. How can a non-physical substance affect a physical one? This objection has existed ever since Descartes described his Cartesian dualism. His proposal that the locus of interaction between the mind and brain is in the pineal gland has long since been discredited. Fodor writes: ‘There are many clear cases of physical causation but not one clear case of nonphysical causation’ (Fodor 1986 p.25). This problem of interaction prompted the development of the aforementioned theories of Property Dualism, Occasionalism and Parallelism.

Furthermore, advances in computing and artificial intelligence continue to erode Descartes’ argument that reason and language are impossible in purely physical systems.

While the argument from introspection appears to be a sound defence of dualism, Churchland neatly destroys it:

...[the argument from introspection] assumes that our faculty of... introspection reveals things as they really are... If one’s pains and hopes and beliefs do not introspectively seem like electrochemical states in a neural network, that may be only because our faculty of introspection... is not sufficiently penetrating to reveal such hidden depths. (p.15)

Despite this, modern-day dualists like Swinburne or Vendler continue to use the arguments from introspection and irreducibility to defend dualism. Vendler writes: ‘...content of experience [is] essentially subjective, thus inaccessible to any public, interpersonal, conceptual system.’ (Vendler 1992 p.318). Although ‘content of experience’ cannot now be examined anywhere but in the brain of the person who experiences it, even if it never can be, there is no reason to assume that it follows different scientific laws to all other physical matter. Fodor aptly illustrates this in his example of psychology: if the mind and its processes differ so much from physical processes, it would follow that the application of scientific methods would be useless in studying the mind (Fodor p.25).

The fact that dualism proposes a non-physical substance that cannot be scientifically studied is a major problem. It is this reason that provoked Dennett to write that:

[The] fundamentally antiscientific stance of dualism is... its most disqualifying feature... It is not that I think I can give a knock-down proof that dualism, in all its forms, is false or incoherent, but that, given the way dualism wallows in mystery, accepting dualism is giving up. (Dennett 1991 p.37)

Does accepting Dualism mean "giving up"?

The reason for which Dennett believes this is because rather than offering an explanation of how the mind works, dualism denies that an explanation can be given. Vendler, one of the key modern-day defenders of dualism, provides the perfect ammunition for Dennett’s attack: ‘I believe that the elements of human consciousness, the buzzing-blooming confusion of our Humean selves are in principle beyond what science can explain.’ (Vendler 1992 p.318). The claim that there are phenomena ‘beyond what science can explain’ seems a foolhardy one in our scientific age, and this is precisely what Dennett is referring to when he writes of dualism’s antiscientific stance.

Vendler, in defence of dualism, discusses the fact that scientists may be able to explain how humans perceive colour and pain but cannot explain the actual experience, what it is like to see a certain colour, or to feel a certain pain (Ibid. p.320-1). This seems perfectly reasonable, but hardly evidence for dualism; current science may have no hope of being able to decipher the overwhelmingly complex brain, but the liver or lungs no doubt appeared just as baffling to the scientists of a two hundred years ago. Quantum physics is currently almost a total mystery to scientists. Many phenomena associated with it cannot be explained by conventional science. No scientist, however, proposes supernatural causes to account for it. There is nothing to suggest that, at the current rate of accretion of scientific knowledge, the brain will remain a mystery for the remainder of human existance.

Swinburne, another well-regarded dualist, claims that ‘...materialism seems to me obviously wrong’ (Swinburne 1986 p.312). In doing so, however, he neglects to mention why dualism is obviously right, and leaves the student of the mind unable to progress in studying it. In allowing the idea of an inexplicable ‘mind’ to explain consciousness and thought, complacency is promoted, and this is precisely what Dennett means in asserting that accepting dualism is ‘giving up.’


During the eighteenth century, chemists believed that fire was composed of a special substance called phlogiston; flammable substances released it when set alight. Science long since proved them wrong, but at the time, it seemed to make sense, and it was easy to believe. Phlogiston provides a good analogy for dualism. The mind, like fire, appears to be a special substance that is like nothing else, elusive, but almost magical. However, so much of the current evidence seems to suggest that the mind, like fire, is simply the product of the physical reactions behind it. This is not to say that the human brain is not a remarkable and enormously complex tool that is capable of incredible things. Ultimately, it may be that the inscrutable nature of human consciousness will forever remain a mystery, but dualism can no longer be held to account for it.

Princess Elizabeth reputedly asked Descartes in 1643: ‘How can the soul of man, being only a thinking substance, determine his bodily spirits to perform voluntary actions?’ (Quoted in Bechtel p. 82).


Bechtel, W. (1988). Body and Mind. Hillsdale: Lawrence Erlbaum.

Churchland, P. (1988). Matter and Consciousness. Cambridge: MIT Press.

Dennett, D. (1991). Consciousness Explained. Boston: Little, Brown.

Fodor, J (1986). The Mind-Body Problem. In R. Warner and T. Szubka eds., The Mind-Body Problem, pp. 24-40. Cambridge: Blackwell.

O’Brien, G. (2001). Dualism. Philosophy of Mind Lecture Notes pp. 3-6.

Swinburne, R (1986). Body and Soul. In R. Warner and T. Szubka eds.,

The Mind-Body Problem, pp. 311-6. Cambridge: Blackwell.

Vendler, Z (1992). The Ineffable Soul. In R. Warner and T. Szubka eds.,The Mind-Body Problem, pp. 317-28. Cambridge: Blackwell.

Warbuton, N. (1995). Philosophy: The Basics. New York: Routledge.

Warner, R (1994). Introduction: The Mind-Body Debate. In R. Warner and T. Szubka eds., The Mind-Body Problem, pp. 1-13. Cambridge: Blackwell.

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