Let me wrap up the week’s blogging by directing you to two essays related to things we’ve been discussing this week.
The first is Mohan Matthen’s review of Thomas Nagel’s book in The Philosopher’s Magazine. I refer you to it partly because it’s an interesting essay in its own right, but also because he seizes on precisely the Nagel quote that caught my attention in this post. Matthen writes:
This is perhaps the moment to come back to the strange pronouncement to which I earlier alluded. Nagel writes, “With regard to evolution, the process of natural selection cannot account for the actual history without an adequate supply of viable mutations, and I believe it remains an open question whether this could have been provided in geological time merely as a result of chemical accident, without the operation of some other factors determining and restricting the forms of genetic variation. It is no longer legitimate simply to imagine a sequence of gradually evolving phenotypes, as if their appearance through mutations in the DNA were unproblematic – as Richard Dawkins does for the evolution of the eye.” (Versions of this claim are repeated at many points in the book.)
Now, this is a scientific challenge to the viability of Darwinian explanation, not just a reflection on its explanatory completeness. The sufficiency of genetic variation to drive natural selection has been a central theme since R A Fisher’s great book, The Genetical Theory of Natural Selection. Nagel, a philosopher, tells us there’s not enough. Big result! But it’s completely unsupported by argument. Nagel says that he would “like to defend the untutored reaction of incredulity to neo-Darwinism … It is prima facie highly implausible that life as we know it is the result of a sequence of physical accidents together with the mechanism of natural selection”. This is just irresponsible. It is simply wrong to adjudicate the probability of mutations by an “untutored reaction of incredulity”. Probability assessments notoriously run counter to common sense. If you think you have a scientifically viable argument, give it, or leave it to scientists to deal with this kind of problem!
That’s pretty close to what I said!
Also interesting is this article by Stephen Cave over at e-Skeptic. He is addressing the question of the soul:
The evidence of science, when brought together with an ancient argument, provides a very powerful case against the existence of a soul that can carry forward your essence once your body fails. The case runs like this: with modern brain-imaging technology, we can now see how specific, localized brain injuries damage or even destroy aspects of a person’s mental life. These are the sorts of dysfunctions that Oliver Sacks brought to the world in his book The Man Who Mistook His Wife For A Hat.4 The man of the title story was a lucid, intelligent music teacher, who had lost the ability to recognize faces and other familiar objects due to damage to his visual cortex.
Since then, countless examples of such dysfunction have been documented—to the point that every part of the mind can now be seen to fail when some part of the brain fails. The neuroscientist Antonio Damasio has studied many such cases.5 He records a stroke victim, for example, who had lost any capacity for emotion; patients who lost all creativity following brain surgery; and others who lost the ability to make decisions. One man with a brain tumor lost what we might call his moral character, becoming irresponsible and disregarding of social norms. I saw something similar in my own father, who also had a brain tumor: it caused profound changes in his personality and capacities before it eventually killed him.
The crux of the challenge then is this: those who believe they have a soul that survives bodily death typically believe that this soul will enable them, like Nathalie in the story above, to see, think, feel, love, reason and do many other things fitting for a happy afterlife. But if we each have a soul that enables us to see, think and feel after the total destruction of the body, why, in the cases of dysfunction documented by neuroscientists, do these souls not enable us to see, think and feel when only a small portion of the brain is destroyed?
That looks like a good argument to me. What do you think? There’s more to Cave’s article than what I’ve quoted, so go read the whole thing!