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February 13, 2004

Changing the Subject...

I have long thought that there is a latent contradiction in the modern scientific world-view.

Consider the following propositions:

A. Adaptive traits of organisms have evolved by natural selection.

B. A trait can only evolve by natural selection if it affects the reproduction of organisms.

C. Any trait that affects the reproduction of organisms has causal efficacy in the physical world, that is, it makes a difference to the state of physical objects (including organisms themselves).

D. Some subjective sensations, such as pleasures and pains, are adaptive traits of organisms.

I think that most biologists would accept these propositions, but I will return to that. Assuming that they are accepted, it follows by elementary logic that:

E. Some subjective sensations have causal efficacy in the physical world.

But here is the latent contradiction in the modern scientific world-view, for that world-view includes the proposition:

F. No subjective sensations have causal efficacy in the physical world.

Propositions (E) and (F) are directly contradictory.

It may perhaps be doubted whether proposition (F) is really part of the modern scientific world-view. It is not a formula of any standard scientific theory, and there are respected scientists and philosophers of science, such as Karl Popper, John Eccles, and Roger Penrose, who have denied it.

But I believe that the predominant world-view of scientists, philosophers of science, and modern analytical (Anglo-American) philosophers would endorse proposition (F). Those, like Penrose, who reject it, rightly see themselves as challenging a prevailing orthodoxy. The majority of ‘orthodox’ thinkers can be classified in one of the following categories:

a) Radical behaviorists, who deny that subjective sensations exist at all;

b) ‘Dual aspect’ materialists, who maintain that subjective sensations are an aspect or property of physical objects, but that those objects behave purely in accordance with physical laws; and

c) Epiphenomenalists, who believe that subjective sensations are a by-product of physical events, and have no causal efficacy of their own.

All three positions imply acceptance of proposition (F). If their implications are rigorously pursued, they also entail:

G. Subjective sensations do not produce or modify other subjective sensations.

For a new or modified sensation would require a change of physical state, and it would contradict proposition (F) if this were produced by another subjective sensation.

It is worth dwelling for a moment on some of the more bizarre implications of propositions (F) and (G). Suppose that you feel a severe pain in your abdomen. You go to your doctor. You tell him that you have a pain in your abdomen. He asks you some questions about the pain and considers your replies. He palpates your abdomen and notes your reactions. He concludes, based on his training and experience, that you have appendicitis. He rings for an ambulance. The ambulance service follows his directions. The ambulance takes you to hospital, with its siren switched on. You arrive at the hospital, and are taken to the OR, where you are given an anaesthetic. A surgeon, using his surgical knowledge and his senses of sight and touch, removes your appendix. When you wake up, the acute pain has gone, but you feel a milder pain from the healing wound, which alerts you to any movements or pressures that might damage the wound and delay recovery.

On a common-sense view of the incident, subjective sensations of one kind or another have influenced the behaviour of yourself and others at every step. Most obviously, it is a subjective pain that has caused you to go to the doctor in the first place, but sensations of sight and hearing also play a major part in the story, for example in the use of a siren to warn other drivers out of the way. Memory and logical thought also seem to influence events, e.g. in forming the doctor’s judgement that you have appendicitis.

Yet on the ‘scientific’ view, as embodied in propositions (F) and (G), all of this is an illusion. Provided that all the physical events (including brain-states) were the same, then the story would run exactly as before, even if none of the participants had any subjective sensations at all. Events would also be the same if physical states produced sensations wildy different from those we are accustomed to, for example if the sensations of appendicitis were ‘switched’ with those of sexual orgasm.

Propositions (F) and (G) therefore seem to defy common-sense, but this is not my main concern at the moment. My concern is their apparent conflict with propositions (A) to (D). Propositions (A) and (B) are themselves part of the scientific world-view. Proposition (C) is merely a terminological clarification. But proposition (D) is more debatable, and my next post will examine it more closely.

Before concluding this post, I should note that the main argument I have outlined is an old one. It is found for example in William James’s Principles of Psychology. But it seems to have been surprisingly little noticed or discussed in the literature on the ‘mind-body’ problem (for an exception see Poper and Eccles, The Self and its Brain, p. 74). I suspect that this is because until recently the great majority of philosophers have had no interest in evolution, or have been actively hostile to natural selection. This is beginning to change, and in the last decade or so there has been a great expansion of interest in ‘consciousness studies’. But from what I have read of this literature, it tends to be preoccupied with what I would call the ‘fancy end’ of the spectrum of mental events, such as human ‘self-awareness’ or even mathematical thought. I think this is the wrong place to start. But more on that later.

Posted by David B at 04:11 AM