Feb 22 2008
Controversies and debates are a great way to learn about logic and the functioning of science. Opponents wrestling over how to interpret the evidence and painstakingly pointing out the logical errors on the other side in a great intellectual exercise. That is primarily why I am enjoying so much my debate with Dr. Michael Egnor, who is writing over at Evolution News and Reviews – the blog of the Discovery Institute, an organization created to promote Intelligent Design.
Today he published his latest response in our ongoing discussion about strict materialism (the mind is the brain) vs dualism (the mind is the brain plus something else undefined). This is his attempt to respond to my direct challenge for him to name a prediction of materialism that has failed. He now claims he has done so, but actually he has completely failed to do so and had instead just added more logical errors to his argument.
Dr. Egnor has two main points in his latest entry. The first is that I am being dogmatic is saying that every prediction of materialism has been validated. Let me put this one to rest. Dr. Egnor is following the general creationist strategy of portraying scientific confidence as dogmatic, he is therefore trying to take the open-minded highground.
First, anyone who has read a significant sampling of my writing knows that I often point out that science is messy, the evidence does not always give a clear answer, and that we must interpret the totality of evidence. Dr. Egnor and I agree that science progresses generally by the preponderance of evidence, that no theory is perfect or complete, and that scientific progress requires constant questioning of prior conclusions.
However, Dr. Egnor is misinterpreting my prior statements to give a different impression. Since I have already corrected him on this I can only guess at his motives for persisting in his accusations. I wrote that:
The materialist hypothesis— that the brain causes consciousness — has made a number of predictions, and every single prediction has been validated.
I stand by this statement. Dr. Egnor, however, has seized upon the “every single” statement and won’t let go. He is claiming that all such statements are dogmatic. His premise is that it is never true that all of the predictions that flow from a scientific theory turn out to be true. This is a critical point – he is claiming that it is never true. I agree that it is generally not the case, but there are times when theories make only true predictions.
This requires specific clarification, because Dr. Egnor has exploited misunderstanding about what I am actually saying. I am not saying that any particular theory is complete, beyond modification, or that there are not deeper levels of understanding. Science generally progresses by deepening, rather than invalidating, prior understanding. Also, this does not mean that every data point of every study or observation will be in concordance. That is a straw man. However, each prediction (once all the data is looked at) will be found to be true.
For further clarification I previously pointed out that I was discussing evidence that “bears upon the basic question of whether or not the theory is true.” This is an important distinction – because often the claim is made that because we have incomplete knowledge of the mechanism of a claim that the claim itself is not true. For example, creationists often point to disagreements about the mechanism of evolution as evidence for doubt about the historical fact of biological evolution. Likewise dualists point to the fact that we cannot currently explain exactly how the brain creates consciousness as evidence that it does not create consciousness. But these are separate questions.
All of this was a huge distraction engineered by Dr. Egnor from the only real point of contention – does existing evidence support strict materialism or dualism? I maintain that it supports materialism – that all of the predictions that flow from the fact of strict materialism that have been resolved have been resolved in the favor of materialism and against dualism. This brings us to the second (and the more important) point in Dr. Egnor’s rebuttal.
Following my prior posts, he writes:
If dualism is true and the mind is partly the product of the material function of the brain and partly the product of something else, then:
1) There will be some mental phenomena without brain function
2) As brain function is altered, the mind will not necessarily be altered
3) If the brain is damaged, then mental function will not necessarily be damaged
4) Brain development will not necessarily correlate with mental development.
5) We will not always be able to correlate brain activity with mental activity – no matter how we choose to look at it
He then goes on to discuss the fMRI study that I brought up in my previous post – a study by Owen et al where they examined thebrain activation in normal controls and a 23 year old patient who was clinically in a persistent vegetative state. The study found the same pattern of brain activation in the subject when compared to normal controls when asked to imagine herself playing tennis and when asked to imagine herself walking through her home.
Dr. Egnor concludes from this:
Dr. Owen’s evidence is in accordance with the dualist prediction. The most parsimonious conclusion was that she was conscious, despite a diagnosis, based on traditional neurological examination, EEG, and neuroimaging, of persistent vegetative state, which is defined as the absence of consciousness. This panoply of neurological tests predicted different — and incompatible — things. Standard brain tests indicated that she had no mind. fMRI testing indicated that her mind was indistinguishable from that of a normal person. Recall that Dr. Novella insists that “every single prediction” of materialism has been verified. That’s not possible with tests that yield contradictory results.
Dr. Egnor’s conclusions are hopelessly wrong on many levels. He is partly playing with words, and partly proceeding from a false unstated major premise. First he says that the patient was conscious despite being vegetative, which is defined as the absence of consciousness. This is subtly deceptive – it excludes the very important fact that clinical diagnoses are based upon clinical criteria, they are not absolute statements about reality. In fact all diagnoses are based upon some criteria – we are always using some method to infer what is really going on. In the case of persistent vegetative state, this diagnosis is based upon the neurological exam – the absence of any evidence on exam of conscious awareness in the patient, while maintaining automatic functions like breathing and roving eye movements.
The neurological exam is not a direct examination of brain function but rather is an examination of reflexes and voluntary actions in order to infer brain function. But neurologists and neurosurgeons typically understand the limitations of the exam. In fact, that is the very purpose of this study – to see if a more sensitive way of looking at brain function displays residual conscious function that the exam cannot detect.
This gets at the major flaw in Dr. Egnor’s entire argument – the various methods of examining brain function are not necessarily “contradictory”, as he claims, but rather the different results reflect their varying sensitivity to brain function. EEG, for example, is a very crude method of looking at brain function (it looks at net electrical activity). The neurological exam is unable to examine the higher cortical functions of a patient if they are not awake enough to follow commands or attend to the exam. MRI scanning shows us only anatomy, and does not look at function.
The exciting thing about fMRI is that it is a new tool that is so far the most sensitive in imaging in detail blood flow and metabolism in the brain, from which we infer brain activity in real time. It is far more sensitive than any previous method, and that is exactly why Owen and his coauthors wanted to see if it revealed cortical activity missed by older methods. To give an analogy of Dr. Egnor’s illogic, this is like saying that if we point a larger telescope at the sky and find objects that were missed by previous smaller telescopes, that the new findings are “contradictory” to the older findings and call into question astronomical theories.
What about his claim that this fMRI study showed that “her mind was indistinguishable from that of a normal person?” This is highly misleading. The study was designed to see if the woman had any residual conscious activity, it was not designed to look at overall brain function. You cannot conclude from this study that her brain function was the same as a conscious person, and therefore consciousness is not completely a product of brain function.
Other fMRI studies, however, have looked at this question. A published review of this question concludes:
Moreover, several studies have reported residual local and specific brain activation patterns in vegetative state patients, whereas long-range neural integration observed during conscious processing was lacking (S. Laureys et al., Brain 123, 1589 (2000). N. D. Schiff et al., Brain 125, 1210 (2002).
So the “preponderance of evidence” that Dr. Egnor champions shows that patients in a persistent vegetative state lack brain activity that is specifically linked to conscious processing. It is important to recognize that the brain is very compartmentalized – different areas serve different functions. It is clearly established that parts of the brain can perform their processing unconsciously and automatically. So it is no surprise that even vegetative patients will retain some subsets of conscious processing.
It is also helpful to recognize that consciousness is not an all-or-nothing state. There is a spectrum of consciousness from fully awake to fully vegetative. It is not uncommon for patients who are barely in what we call a minimally aware state (one categorical notch above persistent vegetative) to be misdiagnosed as being vegetative. The real implications of this study (and the necessary follow up studies – it’s difficult to extrapolate from one case) is that fMRI may be a more sensitive tool for distinguishing subtle or minimal consciousness from no consciousness. Obviously, the neurological exam alone is an imperfect tool for inferring this distinction.
Dr. Egnor has failed to meet my challenge, and his claim to victory is premature. The predictions he laid out for the dualist position have not been validated by his example – Dr. Egnor’s conclusions are based upon the common mistake of failing to add the caveat: within the sensitivity limits of the tools used. This is an important concept in science, and most scientists learn to add this caveat routinely. We see no phenomena -within the limits of this telescope to see, or within the statistical power of this study to detect, etc.
When we look at all the evidence we can conclude that when you damage the brain you damage the mind, when you change the brain you change the mind, and there are no mental phenomena separate from brain phenomena – within the limits of our tools to detect such things.
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