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Thursday, January 05, 2012


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On Edward Feser's blog I was trying to explain how intentionality can be a product of much simpler physical systems than a brain:
http://edwardfeser.blogspot.com/2011/12/reading-rosenberg-part-v.html?showComment=1325138254598#c6023449936579624078 (and following)

That seems to have died out, may as well try to revive the discussion here.

Dr Vallicella,

We agreed elsewhere that for the argument put forward in the post 'The Irreducibility of Intentionality: An Argument From the Indeterminacy of the Physical' to be valid an additional premise needs to be added:

P3. If x is reducible to y, then for every property P (Px => Py).

You think (P3) is true, I think it is not. In the current post you state:

R. Necessarily, for any x, y, if x reduces to y, then it is not the case that y reduces to x.

I agree (with reservations about the case of trivial reduction, i.e. reducing x to x). I will prove that (P3) implies that the relation of reduction is symmetric. In particular, it will show that (P3) => ¬(R). xRy will denote 'x is reducible to y'.

1. Suppose xRy and ¬yRx (for reductio ad absurdum).
2. xRy => (Px <=> Py) (from (P3) by substituting ¬P for P).
3. yRy (by (1) x has the property of reducing to y. By (2) y has this property also).
4. ¬yRy (by (1) x has the property of not being a reduction of y. By (2) y has this property also).

Contradiction. Therefore ¬(1.) and xRy implies yRx. In other words R is symmetric. Does (P3) or (R) give way? I say (P3) on pain of making the notion of reduction incoherent.


Thanks for the comment. You are right about the trivial case of reduction. It can be excluded with a little tweaking of (R).

That's a very clever argument, but an argument that leads to the conclusion that reduction is symmetric has to have gone wrong somewhere.

Suppose we see a particular lightning bolt. That lightning bolt is just an atmospheric electrical discharge. This is an example of reduction: the lightning bolt reduces to the electrical discharge. In reality, the first is nothing other than the second. In reality, there are not two particulars, but one, the first reducing to the second, but not vice versa. Clearly, the electrical discharge does not reduce to the lighning bolt.

This, I take it, is perfectly self-evident. Apparently, you are operating with some idiosyncratic notion of reduction that I simply don't understand.

But I'll think about it some more.


There is a question whether intentionality is found below the level of mind, but that is a huge separate topic. The topic right now is whether mental intentionality and mental states generally are physically reducible.

Dr Vallicella,

I've been clear from the beginning of our conversation about what I think is wrong --- it's (P3). The proof that (P3) => ¬(R) does not depend on any properties of reduction that are not stated in (P3). In other words, the proof is valid for every relation that preserves all the properties of the relata. The only logical choice is to reject either (P3) or (R). (R) is as you rightly say essential to the notion of reduction. Therefore, (P3) needs to go. Do you agree?

Bill, in your para (5) you see reduction as a relation between particulars and this seems to lead to a radical incoherence. I have always thought of reduction as a relation between concepts. For example, earlier in the post you remark that 'the gene got reduced' (presumably to snippets of DNA). What this means to me is that talk of genes, their properties and behaviours was found to be translatable into talk about DNA molecules and their properties and behaviours. This was all very well because genes were previously hypothetical entities put forward to account for the observed facts of inheritance. For all we knew they might be some exotic entity outside the domain of physics and chemistry. But no, they turn out to be molecules of a large and complicated kind but with some interesting symmetries. But there is no sense in which genes are no longer thought to exist. Indeed a gene is now identified with a DNA molecule consisting of a certain sequence of nucleotides. But this is an identity, or better, an equivalence, between concepts, not between particulars, concepts F and G being equivalent when everything that falls under F also falls under G, and vice versa. The asymmetry occurs when one concept is more established as a theoretical posit, or more general, than the other, and the reduction is from the less established/general to the more. But this is a relation between concepts.

Well, if you can show that simpler physical mechanisms than the brain exhibit intentionality, that should go a long way to convincing you that brains can as well.

Or to put it another way: I claim that using a drastically simplified model system is a good way to understand how the mind's intentionality can work. The mind's intentionality may seem like something that couldn't possibly be reduced to a physical machinery. But if you understand how machinery can produce meaning in a simple case, maybe it will seem less magical.

Hi David,

Excellent comment. Kim would like it. In fact, he speaks of reduction in terms of properties which is equivalent to your talk of concepts.

One can of course speak of the reduction of properties to properties. Temperature to mean molecular kinetic motion, etc. But it seems to me that the action is at the level of individuals or particulars. Not only cayusal action but mental 'action.' A mind is a particular, and so is a state of a mind, e.g., my present feeling sleepy, or my present desiring of a cup of coffee.

So it seems that ultimately the physicalist needs a reduction of individuals, e.g., my act of desire to a brain state. After all, properties and concepts are not conscious of anything, are not subjects of experience. By the same token temperature in general is not hot or cold.

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