Saturday, 9 April 2011

Common Sense or Utter Nonsense

By Paul Braterman

Glasgow’s very own Centre for Intelligent Design have been trying to persuade the denizens of Facebook by quoting the philosopher Thomas Nagel. C4ID seem to have been particularly impressed by the following argument:


“Sophisticated members of the contemporary culture have been so thoroughly indoctrinated that they easily lose sight of the fact that evolutionary reductionism defies common sense. A theory that defies common sense can be true, but doubts about its truth should be suppressed only in the face of exceptionally strong evidence.” 
(Thomas Nagel, Philosophy & Public Affairs 36, 187-205, 2008)

It is difficult to see how one could cram a larger number of logical errors into so small a space.

We begin with an extraordinary smear on the writer’s opponents. The more people know, the more firmly they acknowledge the fact of evolution. This, by a populist inversion, is converted into an ad hominem argument against such acknowledgement. The suggestion that doubts are “suppressed” is another smear, based on a pretended ignorance of the robust re-evaluation to which all scientific theories are continually exposed.

Reductionism is not defined in Nagel’s paper (in fact, the passage quoted is the only place where the concept is used), so I don’t know how he is using this notoriously slippery word, nor why purported explanations in terms of intelligent design (the proffered alternative) escape this fate, if indeed they do. However, it is worth pointing out that evolutionary explanations by their very nature describe the behaviour of systems, or even (if we restrict ourselves to the last billion years or so) of interlocking populations of systems, the very opposite of reductionism. I find it shocking that a philosopher of mind, of all people, should be unaware of this.

Worst of all is the appeal to common sense. Common sense is an amalgam of received and unquestioned wisdom, unexamined and often unconscious philosophical assumptions, and extrapolations from everyday experience. What appears to be in accord with common sense must depend on how much one already knows. Thus separate creation of kinds may appear to be in accord with common sense to someone who is completely ignorant of the richness of the fossil record, its relationship to the classification of modern organisms from Linnaeus onwards, the reappearance of the same Linnaean patterns in family trees based on molecular phylogeny, and the overwhelming evidence of the antiquity of the Earth. To someone familiar with these things, it will be the concept of separate creation that violates common sense.

Nagel does not tell us what he would regard as “exceptionally strong evidence”, just as he does not tell us what counts as “evolutionary reductionism”, but the evidence for evolution is presumably strong enough to persuade him to renew his annual flu jab. Since he is writing in a journal concerned with public affairs, it is also worth pointing out that it is strong enough to have led to changes in public policy on the use of antibiotics and pesticides, so as to avoid encouraging the (reductionist?) evolution of resistant strains.

However, the appeal to common sense is an intrinsically weak argument for other, much deeper, reasons. Common sense is an appeal to common experience. Much like the “intuition” discussed in Bertram Russell’s essay on mysticism and logic, it is within the domain of common experience that it has the greatest credibility. Common sense tells us that we are standing still on solid ground, that animals and vegetables are different kinds, that space is Euclidean, that the heavens are unchanging, that an object will eventually come to rest if no force is acting on it, and that tables are solid. That the earth is moving, and that the continents themselves are moving across its surface, that a man shares half his genetic information with a mushroom, that matter distorts the space around it, that the universe is expanding, that a moving object will continue along its trajectory until something stops it, that matter is made up out of atoms and that almost all the mass of these atoms is crammed into a tiny nucleus less than one billionth of the total volume, all of these are violations of common sense. Nonetheless, they are fundamental facts of which any educated person should be aware, even at the risk of being described by Professor Nagel as “sophisticated” and “thoroughly indoctrinated”.

Paul Braterman came into direct contact with Creationism during his time as chemistry professor in Texas, and is now back in Glasgow as an honorary fellow at Glasgow University. His next book, “From Stars to Stalagmites”, will be published by World Scientific in 2011.

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