Notes on John Searle, The Rediscovery of the Mind
Chapter 5

Searle's chapter on reductionism.

1. Emergent Properties

Searle seems to contrast three different relations macro properties ("system features") might have to micro ones.

1. non-emergence: macro properties can be "deduced or figured out or calculated" from micro ones. Examples: shape, weight, velocity.
2. emergence1: "causally emergent system features." The macro properties are not deducible from the micro properties, but may be explainable by them. Examples: solidity, liquidity, transparency.
3. emergence2: macro properties are neither deducible from, nor explainable by, micro properties. Examples: none.

OK, I'm puzzled already. I don't get the difference between solidity and liquidity, on the one hand, and weight or velocity, on the other. As far as I can tell, if we know the facts about the properties of atoms, including the facts about how they interact (all that stuff you learned in chemistry about how many electrons are in which orbitals, etc.), then we can deduce whether a compound will be solid or liquid at, say, room temperature.

I think the reason Searle describes solidity and liquidity as non-emergent is that he identifies solidity with feeling solid, and liquidity with feeling liquid (or something similar). If that's right, then Searle's claim that consciousness is just like solidity, liquidity, etc., is extremely misleading; in the end he thinks that consciousness and only consciousness is emergent.

Searle wants to say that consciousness is explained by neural properties, but not deducible from them.

2. Types of Reductionism

Searle distinguishes between several types of "reductionism."

1. Ontological reduction. Objects of one type are nothing but objects of another type. For example: chairs are nothing but collections of molecules.
2. Property reduction. "a form of ontological reduction, but it concerns properties." [Minor complaint: but S just defined ontological reduction as only applying to objects! Apparently what he wanted was for ontological reduction to be a generic category, with object reduction and property reduction as species.] Example: temperature is mean molecular kinetic energy. [Another minor complaint: Searle says "heat" instead of "temperature," but this isn't quite right.]
3. Theoretical reduction. The laws of the reduced theory can be deduced from the laws of the reducing theory. Example: reduction of the gas laws to the laws of statistical thermodynamics.
4. Logical or definitional reduction. Terms for macro properties or things are definable by means of terms for micro properties or things.
5. Causal reduction. The causal powers of the reduced entity are explainable in terms of the causal powers of the reducing entity.

Searle says that historically, causal reductions tend to lead to ontological reductions, but he suggests that this is often accomplished by "redefining" what we're trying to reduce. But this general pattern doesn't work in the case of consciousness.

I think this "redefining" interpretation of reduction is peculiar. As far as I can see, "reducing" temperature to mean molecular kinetic energy doesn't involve redefining anything. It's true that one way in which we identify heat is by way of our experiences: we attribute higher temperatures to things that feel hotter. But we never did define heat as "experiencing heat sensations" or anything similar: rather, we've always thought of heat as the cause of heat sensations. When we find out that heat sensations are caused by molecular kinetic energy, we realize that this is what heat is, and this doesn't involve any sort of redefinition at all.

So Searle's view is that consciousness is reducible in sense 5, but not in any of senses 1-4.

It seems pretty odd to call 5 "reduction" at all! This seems needlessly confusing, especially since Searle immediately goes on to say that consciousness is "irreducible."

3. Why Consciousness is Irreducible

We can't reduce pain in the same way we can color.

Color: we have color experiences, and these are caused by external-world phenomena (light absorption and reflection). We reduce color by identifying it with the causes of our color sensations, and thus carving it off from the sensations themselves.

Pain: we can't do anything similar. We have pain experiences, and these are caused by physical phenomena (stimulation of certain nerves, for example). But we can't carve off the neural causes and claim that we've reduced pain. Why not? Because pain is a term for a certain kind of experience, not for the causes of that experience.

4. Why Irreducibility Has No Deep Consequences

Searle thinks that although consciousness is irreducible, this is true "for a trivial reason," that it "is a trivial consequence of the pragmatics of our definitional practices" (122).

This relates back to his "carving off" interpretation of ontological reduction (including property reduction). He thinks that reduction proceeds by carving reality off from appearance. But conscious experience is appearance, so it makes no sense to carve it off from appearance.

"We did not really eliminate the subjectivity of red, for example, when we reduced red to light reflectances; we simply stopped calling the subjective part 'red'" (123).

I don't think red ever was subjective. We didn't redefine anything. 'Red' always was a term for the cause of "red" experiences, and we found out what this cause is. (But possibly this is open to debate; and in any case, there are other terms for sensory properties, like 'taste', where I think the term may be genuinely ambiguous.)

Searle's conclusion (p. 126): "It seems to me obvious . . . that macro mental phenomena are all caused by lower-level micro phenomena. There is nothing mysterious about such bottom-up causation: it is quite common in the physical world."

To me, this seems about as wrong as it's possible to get! This kind of bottom-up causation is unheard of in the physical world (with the possible exception of brain-mind connections). The relation between micro and macro properties is not causation but reduction. The only way Searle can make it seem otherwise is by building consciousness into supposedly physical properties like liquidity or solidity. So if it's in fact true that mental properties are caused by, but not reducible to, micro level physical properties, this really would be a unique and rather radical fact.

Last update: August 30, 2009. 
Curtis Brown  |  Philosophy of Mind   |  Philosophy Department  |   Trinity University
cbrown@trinity.edu