Mind and Body

1 The mind-body problem

A human being has a body, made up of elements which are purely physical.  The body is no doubt a fantastically complex physical item, but it is a physical item nevertheless.  It is made up of cells of various sorts, which in turn are made up of complex molecular structures, which in turn are made up of atoms, and atoms are clearly physical items.  We can affirm, then, that:
 
 (1) The human body is a physical thing.
It is also evident that each human being has a mental life.  We have thoughts, sensations, emotions, desires, and so on.  That is also beyond doubt, because by doubting it you would thereby demonstrate you had a mental life: for doubting itself is an activity of the mind.  In order for us to indulge in such mental activities it seems that we must have minds.   Many people believe that the mind is not a physical thing, and on the face of it they have reason for this belief.  Physical objects can be weighed, measured, located in space; their physical components have a definite physical structure, and so on.  But it does not seem to make sense to ask exactly how much the mind weighs, exactly where it is located, how much space it takes up, what its physical components are.  If the mind is made up of anything it is made up of thoughts, sensations, emotions, and so on, and these don't seem to be the sorts of things about which such questions can be sensibly asked either.  These considerations suggest:
 
 (2) The human mind is not a physical thing.
Suppose I want to show you that the mind and the body interact.  I deliberate about how to do this and I decide to do so by raising my arm. I will my arm to rise and it duly goes up. Light reflected from my arm travels to your retina, stimulating the  rods and cones in your eyes,  which in turn create a fantastically complex burst of neural activity in your visual cortex, and then you see my arm rise.
    So, some m ental events (deliberating) cause some other mental events (willing) which in turn causes some physical events (my arm's rising) which causes some other mental events (yours seeing my arm go up).  It just seems obvious that there is a rich network of causal interactions between the mental and the physical.
 
 (3) The mind and the body causally interact.
So far so good.  Now we turn to science, and we find that the natural sciences (physics, chemistry, biology, physiology etc.) appear to deal exclusively with purely physical items.  And for the most part the laws that these sciences have discovered have dealt exclusively with causal interaction between purely physical items.  Admittedly these sciences are far from complete, and admittedly we do not have complete accounts within these sciences of even the simple arm-raising episode mentioned above.  Still, scientists are generally confident that the full scientific description of that episode would involve just the fundamental physical laws which deal only with purely physical substances.  In the the scientific account of nature presented to us by the natural sciences, physical substances interact only with other physical substances.  There is no provision in the statement of these laws for physical events to bring about mental effects, nor for physical events to be affected by mental events.  So on the basis of the scientific picture of the world many would be confident that:
 
 (4) The physical and the non-physical do not causally interact.
We now have a problem, for not all of (1), (2), (3), and (4) can be true.  If (1), (2) and (3) are true then (4) is false.  If (1), (2) and (4) are true (3) is false.  In general, if any three of them are true, then the fourth is false.  This is what is known as an inconsistent tetrad ('tetrad', because there are four of them).  In order to avoid an inconsistency we have to give up at least one of these propositions.
 

2 A plethora of theories

If we cannot rationally believe all of the propositions (1), (2), (3), (4) then we have to abandon at least one of them.  There are a number of choices, and different attempted solutions to the mind-body problem arise from these different choices.  (Sometimes philosophers are accused of not providing answers: the truth is that there is no shortage of answers at all.  If there is a problem about our answers it is that we provide far too many!!)  What we are interested in here is evaluating the different theories that have been put forward.  But before we get into a detailed discussion of those, it will be helpful to characterize the different theories in terms of their solution to the above logical problem: each theory solves the problem by rejecting one of (1), (2), (3), (4).  There are two main kinds of theories: dualisms (those that accept that the mental and the physical are quite different) and monisms (those which deny there is a fundamental division here).
 

2.1  Dualisms

If you accept both (1) and (2) then you are committed to some kind of dualism: the doctrine that there are at least two kinds of things, physical things and nonphysical things.  Then you have a choice of either
 
         (a)  endorsing (3) and rejecting (4);
or    (b)  rejecting (3) and endorsing (4).
The position (a) is called dualistic interactionism: there are two sorts of things, the mind (non-physical) and the body (physical), and these two sorts of things causally interact.  Position (b) takes a variety of forms.  The rejection of interactionism, (3), can be either partial or total.  To see this note that (3) divides into two parts:
 
 (3.i)   Changes in the body cause changes in the mind.
 (3.ii)  Changes in the mind cause changes in the body.
The total rejection of both 3.i and 3.ii is usually known as parallelism: the mind and the body work in parallel, but without any causal interaction.  However, a different position arises from the acceptance of 3.i and the rejection of 3.ii.  The body affects the mind, but the mind has no causal power over the body.  This position is usually known as epiphenomenalism.
 
 

2.2  Monisms

Monism (teh doctrine that there is really must one fundamental stuff) fall into two broad categories: Physicalism and Idealism.
 
Physicalism affirms (1) and denies (2).
The characteristic doctrine of physicalism (or materialism) is that, at bottom, everything is really physical.  According to the physicalist, what we think of as the mind is ultimately constituted out of purely material elements.   There are various kinds of physicalism but they all share this common doctrine: that a complete account of the physical universe would thereby be a complete account of the universe.  There is no extra story to be told, once we have told the whole story about the purely physical parts of the universe.
 
Idealism denies (1) and affirms (2).
The characteristic doctrine of idealism is that, at bottom, everything is really mental.  According to the idealist, what we think of as physical objects (including our own bodies)are ultimately constituted out of purely mental elements (namely, the ideas in people's minds).   This is an interesting thesis which we will look at more closely in the next section of the course.