Thursday, September 13, 2007

On confusing reduction with elimination

This summary I wrote from an old post helps explain the relation between reduction and elimination, since that came up in a discussion here.

The Churchlands wrote an essay entitled “Intertheoretic Reduction: A Neuroscientist’s Field Guide,” in On the Contrary: Critical Essays 1987-1997 (Cambridge, MIT Press, 1998) in which they distinguish three types of intertheoretic reductions: conservative, reforming, and eliminiative. The reduction of temperature in a gas to the mean kinetic energy of the gas’s molecules was a conservative reduction, in that it doesn’t require us to reconceive temperature in any radical way in order to view it as the MKE of the molecules. The secondary qualities of temperature, how it feels, are not denied, they are simply pronounced to be the way we react to temperature rather than something in temperature itself. If the concept of temperature was essential to the meaning of our lives, this type of reduction would not threaten us in any way.

The second type is a reforming reduction, which shows that an earlier theory had significantly misconceived the phenomena it covered. Newtonian mass is replaced in relativity theory with mass relative to a frame of reference, but we were not just dead wrong when we used the concept of mass.

The most radical is an eliminative reduction. In this, the old idea is so wide of the mark that it is simply deleted by the new theory. No single has does the work of phlogiston, but phlogiston is replaced by a theory that distinguishes between oxygen, carbon monoxide, and carbon dioxide.



At 9/13/2007 06:02:00 PM , Blogger Doctor Logic said...

Thank you for posting this! The examples expose the real issue with the concept of eliminative reductionism.

Temperature is something that is sensed more or less directly. Temperature is not an explanation.

Mass (or, weight, at least) is also directly sensed. It is not an explanation.

Phlogiston isn't sensed. Combustion is sensed. Phlogiston is an explanation for something sensed (the combustion), and one that happens to be incorrect.

This is the problem that I perceive with eliminative reduction (ER) in the cases where it is generally used.

The concept of ER is usually invoked when we think that something directly experienced is being counter-intuitively washed away by the reduction. However, I don't think can happen.

We have direct sensations and feelings. If those sensations are explained by a physical theory, they don't get eliminated. Rather, they get predicted. The only thing being eliminated are competing explanations that don't fare as well.

Let's look at free will in particular. Here' I'm talking about free will as a sensation or direct experience, not as an explanation for experiences.

The direct experience of free will is this: I perceive a selection of possible actions, I predict the outcome of each possible action, choose the action that I prefer, and see that my choice generally results in the intended effect. In this way, my choices have made a difference, and I have displayed apparent agency.

If my thinking process and my preferences were explained by a material mechanism, this direct experience is unaltered. The direct experience is simply explained in terms of a prediction of physics. Free will is not eliminated.

What is eliminated? What is eliminated is the "idea" that there is some alternative to determinism and randomness known as "free choice". Yet this idea is not a direct experience. We don't directly sense that the world is non-deterministic. Rather, "free choice" is a supposed explanation for our actual experiences. (I hesitate to call "free choice" an explanation because it is neither predictive, nor logically coherent.)

So, a mechanistic theory of mind does not eliminate direct experiences free will. It eliminates a faulty and incoherent explanation for those experiences. And it is the role of every good explanation to displace poor ones.

At 9/13/2007 10:54:00 PM , Blogger Blue Devil Knight said...

Do they actually use the term 'eliminative reduction'? That sounds very strange given everything Paul has written on the subject.

At 9/13/2007 11:25:00 PM , Blogger Victor Reppert said...

In an "eliminative reduction," don't you still have a reducing theory and a reduced theory?

At 9/14/2007 12:10:00 AM , Blogger Blue Devil Knight said...

VR: I am mostly curious about whether they actually used the term. It sounds like an oxymoron to me.

The theory that is eliminated is not reduced, so it just seems wrong to say that a theory underwent eliminative reduction. The theory was eliminated, replaced by another theory (and the replacing theory may or may not be reducible to the theory describing the lower-level goings-on).

E.g., the vital force was eliminated, not reduced, even though it was never pushed aside by a theory at the same level. Simply learning the lower-level details was enough to know that vitalism should be eliminated. So did vitalism undergo an eliminative reduction? I don't think so. I don't think any theory does.

But again, if they used that terminology I stand corrected. It would just be a pretty major change from Paul's earlier writings. I don't have the On the Contrary book so I couldn't check.

At 9/14/2007 08:39:00 AM , Blogger Blue Devil Knight said...

It's kind of funny, given the title of the post. :)

At 9/17/2007 12:10:00 PM , Blogger Victor Reppert said...

It looks like the terminology was invented by Angus Menuge, in Agents Under Fire, from whom I drew the account. I hadn't noticed that he had introduced the terminology the first time I read it.

The idea I had was to argue that you couldn't automatically argue that if the metal was reduced, it would no longer be thought to exist.

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