I recently
ran across this post by neurologist Dr. Steve Novella over at his blog Neurologica. The post is basically a
rebuttal to neurosurgeon Michael Egnor’s views regarding how memory is encoded
in the brain; however, my agenda here is not to comment on this exchange.
Rather, this current post of mine was sparked by comments made by Dr. Novella
in his post regarding the nature of the mind. Here’s some of what he had to
say:
As I have pointed out numerous times myself – mental phenomena are functional active things. They are based in the physical substance of the brain, but they are not just the physical substance – they are what results from the function of the physical substance. The mind is what the brain does.
I’ve heard this theory of mind put forward many times; that is, the theory that the mind just is what the brain does. Note that this is not the same as saying that the mind is identical to the brain, rather it simply says that psychological states just are the products of neurophysiological processes. This theory is simply a type of identity theory. Identity theory is a type of reductive materialism and is defined, by the Stanford Encyclopedia of Philosophy, as the theory that “states and processes of the mind are identical to states and processes of the brain.” And this seems to be exactly what Dr. Novella’s position is, for he says that “mental phenomena (including memory) do not simply correlate with the firing of neurons in the brain – they are the firing of neurons in the brain.”
The first step that most materialists take towards justifying identity theory—or really any variation of a materialist philosophy of mind—is to provide evidence from neuroscience that demonstrates that the brain and mind are intimately related. And needless to say this evidence is not lacking at all. We know quite well that altering brain chemistry and brain structure can subsequently alter personality, can create a “divide” in consciousness, and can even cause individuals to fail to recognize familiar objects or even loved ones. There is no doubt that this says much about the correlation between the mind and the brain, but does is say any more than that by itself? Not really. Philosopher of mind James Madden, in his book Mind, Matter and Nature, articulates:
Has neuroscience revealed an empirical identity between psychological states and brain states? It clearly has not, nor does it seem that it ever could. What neuroscience does is to provide us with ever more precise descriptions of the goings-on in our brains that are correlated with our psychological states[…] Correlation is a far cry from identity; two phenomena can be perfectly correlated, without being identical. (p. 108)
Intentionality and Necessary
conditions
One of the
first problems that identity theory runs into is accounting for intentionality. In philosophy of mind,
intentionality refers to the ability of something to be about, or refer to, or
represent something beyond itself. When I think of my wife, my thought is about, and refers to her. Now the problem here is that physical things only
exhibit derived or secondary intentionality. The written
word “cat” only refers to a cat if a mind so interprets it that way. It could
just as easily have been the case that we endowed the word and utterance “cat”
with a completely different meaning, or that another group of individuals takes
the word or utterance “cat” to mean love. This means that physical symbols only
have extrinsic intentionality and
derive their intentionality from a mind that already exists. Now note that
psychological states that exhibit intentionality do not borrow this
intentionality from somewhere else. That is to say, our thoughts are not
intentional because something external to us interprets them, rather they
exhibit intrinsic intentionality, and
thus our mental states constitute intentionality that is completely opposite
the physical.Now this posits problems for any philosophy of mind that is primarily materialistic. For how can a physical process be that which grounds intentionality if the physical first needs a mind in order to have intentionality at all? The materialist, then, needs a mind in the first place before he can start talking of intentionality being present in the physical. But the mind is the very thing the materialist is attempting to account for!
Furthermore,
things get even worse for the identity theorist than this. Let us imagine a
scenario where I raise my arm to a certain trajectory T1. Now let us say that I
intended to raise my arm for some specific reason—perhaps to greet a co-worker.
Now an identity theorist would say that my act of raising my arm can be
accounted for in specifically neurophysiological events which terminated in certain
muscular events which caused the raising of my arm. We can call this physical
sequence that leads to the raising of my arm X1. Note that X1, by itself, is a
sufficient condition for the raising of my arm to trajectory T1. So, the
raising of my arm is therefore accounted for in completely materialist terms
right? Not necessarily. For now
imagine that instead of the physical sequence X1 causing T1, we say that this
physical sequence is altered by only one neuron to cause a slightly different
trajectory in my arm raising. So we can call this different physical sequence
X2, and this new trajectory T2. So now we can say that X2 is a sufficient
condition for the raising of my arm to trajectory T2.
But this
is where we run into problems. While X1 might be sufficient for raising my arm
to T1, and X2 is sufficient for raising my arm to T2, X1 and X2 are not necessary conditions for raising my
arm as an intentional act. That is, in order to raise my arm as an intentional
act, I do not need X1 or X2, but could have some other physical sequence
obtain. But this means that no specific
physical act is necessary for explaining the intentional act of raising my arm!
Rather, while physical processes are sufficient for explaining my arm being
raised in a certain specific manner, they are not sufficient for explaining my
arm raising as an intentional act. Now note that if psychological states just
are neurophysiological processes (i.e. if the mind is what the brain does),
then certain physical sequences would be sufficient and necessary conditions for raising my arm intentionally. And
since this is not the case then it cannot be true that our psychological states
just are processes in the brain.
Rationality
A second
problem that confronts identity theory is that of rationality. When certain neurophysiological states in the brain
are followed by other subsequent neurophysiological states, neurologists
understand exactly how these states follow from one another. If S1 (a
neurophysiological process) is followed by S2, which is then followed by S3, it
is the electrochemical properties of the brain, ultimately grounded in physical
laws, that cause this transition. Now imagine that I entertain the following
line of thought: 1) John is usually late to class on Mondays, 2) It’s Monday,
3) Therefore, John will most likely be late to class. Now notice that, on
identity theory, each thought (each psychological state) will correspond to a
certain brain state (neurophysiological process). But this means that if
identity theory is true, then the cause of me inferring 3) from 1) and 2) is simply
the electrochemical properties associated with those brain states.
This
obviously runs into problems. For my act of inferring 3) was due to the semantics
associated with 1) and 2), and I simply saw logically that 3) follows. And, in
fact, for any inference or conclusion to be considered rational, it needs to be
caused by the meaning and semantics of previous thoughts, or propositions. But,
again, this is not true on identity theory. On identity theory it is not the
semantics of 1) and 2) that cause the mental state of 3), rather what causes 3)
is simply the blind electrochemical properties of the neurophysiological state
associated with 2), which was caused in the same way by 1). But this type of
causation is purely blind deterministic efficient causation. That is, it is
simply matter dancing to the tune of physical laws, and therefore cannot be
called rational in any sense. Thus
stated, on identity theory any type of “rational inference” is, upon closer
inspection, only pseudo-rationality, and therefore rationality as such is only
an illusion.
Note that
these are not the only devastating critiques of identity theory (there are others that I've put forth here and here). But I believe
they go a long way in demonstrating that this reductive materialist theory of
mind—that the mind is what the brain does—is
vacuous. Now let it also be noted that the arguments above are not
soul-of-the-gaps arguments. That is, the arguments are not saying “this or that aspect of cognition is difficult to
explain currently, so we need to posit the soul or some Cartesian substance to
account for them.” Rather the above arguments are ontological and deductive.
That is, they don’t argue from current scientific ignorance, but instead argue
that the ontology of a materialist theory of mind cannot ever in principle solve these problems. These
problems then are a sort of reductio ad
absurdum of materialism, and thus findings in neuroscience are irrelevant
here.
In
conclusion, then, we see that identity theory rests on a conflation of
correlation with causation, and faces insurmountable arguments that demonstrate
that the mind cannot simply be “what the mind does.”