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Are minds are bodies distinct kinds of substances?
The idea that minds and bodies are two distinct substances is famously associated
with Descartes. The conclusion that the mind and body are separate can be reached by
considering the view point of a radical sceptic. All the information we have about the
world is bought to us through our senses. They are the only way we can receive
empirical knowledge, and all our methods of checking their information also rely on
them. Also, we know they can be deceived and often are. The railways lines that seem
to meet at a point somewhere on the horizon do not meet at all. By making further
observations, by walking down the track or thinking about how train run we can
easily tell that the appearance of the lines meeting is only an optical illusion, and we
dismiss it. Anomalous results are discarded to make the most coherent view of our
world possible. But the possibility remains that if we could be deceived in one
respect, that we could be deceived in many. In fact, Descartes suggested, we could be
deceived in all our perceptions. There is no proof that all our perceptions are provided
to us by an ‘evil genius’, and that
the earth, colours, figures, sound and all other external things are nought but
the illusions and dreams of which this genius has availed himself in order to
lay traps for my credulity.
(Descartes in Book 5 p158).
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Faced with this uncertainty Descartes falls back to the cogito, his famous statement of
the one thing we can be sure of: ‘I am, I exist, is necessarily true each time I
pronounce it, or that I mentally conceive it.’ (ibid. p161).
This is where dualism starts. While the existence of your mind is safeguarded by the
cogito, your body is not. Even your knowledge of your body comes through your
senses, and so can be doubted. The mind’s existence can be proved a priori, before
reference to the outside world, the body cannot. Adding the reasonable premise that
concepts whose existence must be proved separately are separate concepts, a divide is
drawn between the mind and the body. Descartes did go on to argue for the existence
of his body, based on his ‘clear and distinct’ (ibid. p175) impression of it. However,
he perceives the distinction between his mind and body just as distinctly. In
meditation VI Descartes describes more exactly how this distinction manifests itself.
The mind is a substance the essence of which is to think. Substance in this instance,
and throughout this essay, will be taken to have Descartes’ meaning as ‘a thing which
so exists that it needs no other thing in order to exist.’ (ibid. p23). The essence of the
mind-substance, Descartes argues, is thought. To have a mind without thought is
incoherent, thought is what makes a mind a mind. If a thing has thought then it is a
mind, if it does not then it is not a mind. The essence of the body-substance and of all
physical things, Descartes says, is physical extension. To have extension makes
something a physical object, and an object without extension cannot be a physical
object at all.
To this framework of two substances must be added further observations of the
appearance of the world. For instance, my experience is available to me in a unique
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way. I sense my pain in a way that no-one else can, and no-one else can sense my
pain. Also this pain is directly felt, not just observed. In the film Terminator 2, the
character of the robotic assassin describes ‘I sense injuries. The data could be called
pain.’ (Terminator 2, 1991) The Terminator’s passive experience is not the experience
of people. Pain hurts! This means that minds must have a distinctive link with one
body and one body alone, and that raises the question, what form can this link take?
While Descartes gives little description of the nature of the mind-substance, it is clear
that it is not physically extended. How something without a physical presence can
interact with the physical world was made clear neither by Descartes, who simply
asserted the link, nor by subsequent thinkers. Both the necessity for this link and its
mysteriousness are inherent in a dualist theory, and extends in both directions: not
only must pain and sense information somehow reach my mind from the physical
world, but my responses must reach the world. Everyday experience seems to show
that when I decide to move my arm, my arm moves. Information flows to and from
the mind, somehow bridging the physical / mental divide.
The dualist divide also comes under fire in a less rigorous way from the principle of
Ockham’s razor. It is a principle rather than a hard and fast rule, but can be expressed
as ‘don’t multiply entities beyond necessity’ (Thinking from A to Z, p97). In this
case, materialists argue, there is no need for a second substance when the material
world is all that is necessary. Materialism has no problem with associating pain and
feelings especially with one body – your brain is only attached to one body, so that
body’s pain is all it will ever feel. The links between the brain and body are readily
examinable to anyone with a corpse and a scalpel. The issue then becomes, can
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collections of atoms in the material world really account for our subjective experience
of the world?
One of the greatest inconsistencies levelled at material monism is associated with the
materialist treatment of qualia. Qualia are our sense experience; the colour red, the
smell of a cooked pizza, the texture of paper between your fingers are all qualia, they
are the sensations that make up your view of the world around you. They are
subjective, they are your own experiences and as such it seems at first as though noone else can experience them as you do. There appears to be no guarantee that what I
see as red you see as blue, although you attach the label ‘red’ to it, just as I do. We
would both agree that the top traffic light is ‘red’, although the sensations we have are
different.
Looking more closely, though, this form of inversion is not so simple. There are
various aspects of colours which everyone agrees on but which preclude this form of
inversion. For instance, you cannot have a greenish-red colour. You can have reddishyellow, and yellow-green, but not greenish-red. That’s universally acknowledged, and
may seem like an arbitrary limitation until you consider the wavelengths of
electromagnetic radiation that cause what we call colour. Red is a lower wavelength
than yellow which in turn is a lower wavelength than green. So instantly you can see
that greenish-red isn’t possible, both of those colours fade into yellow first. So
imagining a person who’s see red as blue but is otherwise identical suddenly problem
problematic - he should have no problem seeing a greenish-red, for him it would be
greenish-blue but physically it cannot happen. Conversely he should be able to
imagine a bluey-orange colour with no difficulty, and he may be puzzled as to why
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there are no instances of it in nature. Qualia and the material world are much more
closely linked than dualism can allow for; in dualism, where colours exist ‘freely’ in
the mind artificial explanations are needed for the absence of greenish-red and other,
similar, limitations.
A further criticism of materialism is based on how these qualia could exist within a
brain. This is demonstrated by the China Brain thought experiment. This experiment
imagines that the individual people of China are persuaded to act as neurones. Each
can signal to others around him via radio in a manner completely analogous to
neurones firing. In fact, the entire arrangement in entirely equivalent to the
arrangement of neurones in the brain and can then be attached to a dummy that
provides sense input and moves like a person. Combine this set-up with the materialist
premise that minds are purely physical, and it follows that the China brain we have
created should be able to think and feel in exactly the way we do, it should be entirely
equivalent to a person. It should be able to know the colour red and get angry,
confused and happy just as we do. However, the argument runs, as the China brain
clearly does not have any knowledge of red, or the smell of a rose or any other quale,
the materialist view must be incomplete.
The problem here is with the premise that qualia cannot exist within this collection of
people. Qualia are no less likely to exist with a collection of people than they are to
exist within a collection of neurones, so to deny that they exist in the China Brain is to
beg the question. To put that question explicitly: can sense experience exist in a
wholly material system? To argue that qualia can exist in solely a brain seems to leave
no way of denying that qualia could not also exist in the China Brain, a Star Trek
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plasma cloud or a computer system. Personally, this seems to me to be the next
logical step in the long history of showing that humans are nothing special. In the time
of Aristotle it was thought we lived at the centre of the universe and were a species
created in God’s image. Newton and Darwin respectively showed that neither our
planet nor our species was anything other than an unimportant example of the wider
workings of the universe. The desire to hold our minds as something special seems to
spring from that same egotism and, while there is no empirical evidence to show how
ethereal concepts like qualia, self-consciousness, guilt or grief could exist in a brain,
the precedent for explanation is good.
I have defended materialism against the China brain thought experiment and against
the qualia inversion argument, and I have highlighted the problem of communication
between the substances in dualism. But the first argument for dualism remains, the
foundation, the bedrock, the cogito.
It has been claimed that Descartes relied on an un-stated premise in his famous axiom,
namely that thoughts require a thinker. The ‘I’ of ‘I am, I exist’ then becomes the very
thing Descartes is trying to prove, and hence that he is begging the question. A better
rendering, it is suggested, is ‘there are thoughts’. Simply by using fewer words this
takes a step away from contention, and this new rendering gives new possibilities. As
thoughts are less mysterious than an ‘I’ they do not necessarily need to dwell in a
different substance; they could be housed in a brain, and might even eventually be
open to investigation by science. Certainly Descartes has succinctly put an incredible
and undeniable certainty, but the exactly form of that certainty must be carefully
examined, and the consequences of it are by no means clear.
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While both materialism and dualism have problems that need to be overcome it seems
that progress can only be reasonably made to resolve the materialist dilemmas.
Because of that, and the intuitive lure of Ockham’s razor, I conclude that minds and
bodies are not distinct substances.
Word Count:
1870
Bibliography
Nigel Warburton (2000) Thinking from A to Z, Routledge
Robert Wilkinson (1999) Minds and bodies, The Open University
James Cameron (1991) Terminator 2: Judgment Day,
Simon Blackburn (1999) Think, Oxford Univeristy Press
Martin Hollis (1997) Invitation to Philosophy, Blackwell Publishing
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