Jackson on Popper on materialism

While we’re on the subject of mind-body interaction, let’s take a look at Frank Jackson’s article on Karl Popper’s philosophy of mind in the new Cambridge Companion to Popper, edited by Jeremy Shearmur and Geoffrey Stokes.  Popper was a dualist of sorts, and Jackson’s focus is on the role Popper’s “World 3” concept and the issue of causal interaction played in his critique of materialism.

First, a brief summary of the World 3 idea (which I discussed in a post some years back).  Popper distinguished between three “worlds” or compartments of reality.  World 1 is the realm of physical objects and processes, such as tables and chairs, rocks and trees, molecules and atoms, stars and galaxies.  World 2 is the realm of thoughts, experiences, and mental phenomena in general.  World 3 is the realm of concepts, theories, arguments, stories, institutions, and other abstractions that have a kind of reality over and above both the physical entities that represent them and the thoughts we have about them.  For example, the Pythagorean theorem and the theory of relativity don’t go out of existence when we stop thinking about them and would not go out of existence even if all the books and articles discussing them were destroyed.

Popper’s World 3 is in some respects reminiscent of Plato’s realm of the Forms, but differs in that Popper takes World 3 to be something man-made.  As I noted in the earlier post just linked to, this makes his positon at least somewhat comparable the Aristotelian realist (as opposed to Platonic realist) view that universals are abstracted by the mind from the concrete objects that instantiate them rather than pre-existing such abstraction.

Naturally, all of this raises questions about the ontological status of the three Worlds, and Popper’s view is that they are irreducibly different, which is one reason he is not a materialist.  One reason this irreducibility would support a rejection of materialism is that if World 3 objects are abstract entities rather than material objects or processes, then it is false to say, as the materialist does, that the material world is all that exists.

Now, as Jackson notes, a materialist could respond to this by modifying his materialism.  He could allow that there are immaterial or abstract objects and thus admit that the material world is not all that exists, but still insist that the mind is entirely material.  That is to say, he could argue that World 2 is reducible to World 1 even if World 3 is not.  But as Jackson also notes, Popper thinks that there is a problem with this strategy posed by the existence of causal interaction between the mental and the physical.

Materialists, of course, often claim that their position can better account for such interaction than Cartesian dualism can.  Consider the case of a sensation of pain which is caused by damage to the body and in turn causes wincing and moaning.  If this sensation occurs in a Cartesian res cogitans, the materialist says, then we have to face the mystery of how an immaterial substance gets into causal contact with a material substance like the body.  But if we suppose that the sensation is just a kind of brain process, then (the argument continues) its causal interaction with the rest of the body is no more mysterious than is the causal interaction between any other two physical things. 

Popper’s response is that at least some World 2 entities, and indeed the most interesting ones, involve (as a sensation of pain does not) causal relations to World 3 entities no less than to World 1 entities.  For example, when you entertain a thought about the Pythagorean theorem and then write the theorem down on a piece of paper, we have a causal relationship between a World 1 entity (the paper) and a World 2 entity (your thought) but also a World 3 entity (the theorem).  And since the World 3 entity is immaterial, the materialist is hardly going to have a better time accounting for its relationship to World 1 than the dualist has accounting for the relationship between World 2 and World 1.  And of course, there are a great many mental states that involve relations to World 3 entities (theories, concepts, arguments, etc.).  Hence the materialist claim to be better able to account for mind-body interaction is greatly oversold.

A related problem for materialism posed by World 3 is that the materialist typically holds that World 1 is causally closed.  Hence, since we interact causally with other World 1 objects, we must (the materialist concludes) be part of World 1.  Yet since World 3 entities influence World 1, World 1 cannot be causally closed after all.  Thus does a central argument for materialism collapse.  There is no reason to insist on causal grounds that World 2 must be material if we know that World 3 is immaterial and yet causally interacts with World 1. 

Obviously a materialist could try to respond by simply denying the reality of World 3, but something like World 3 must be accepted on pain of taking on all the problems afflicting nominalism, conceptualism, etc.  Jackson suggests another response, but it is (with all due respect to Jackson) a very bad one.  He writes:

[I]t is not at all obvious that there is a special problem for materialism here.  Is it easier to understand how a state in ectoplasm’s standing in a relation to an abstract entity can have causal effects in World 1 than it is to understand how a state of a material brain standing in such a relation can have causal effects in World 1?  How could the switch from material to ectoplasmic instantiation help?  (p. 279)

This seems to have become a stock move among contemporary materialists.  For any dualist argument to the effect that qualia, or the intentional content of a thought, or whatever cannot be accounted for in material terms, the materialist responds that the same arguments would, if correct, show also that these mental phenomena cannot be accounted for in terms of the “ectoplasm” allegedly posited by the dualist. 

The trouble with this, of course, is that no prominent dualist philosopher (nor any non-prominent one, as far as I can tell) is in fact committed to the existence of “ectoplasm,” whatever that is supposed to be.  This is a straw man.

I have in earlier posts discussed the way a straw man of this sort has been attacked by Daniel Stoljar and by Paul Churchland.  (In Churchland’s case, ironically, his remarks were aimed at the “knowledge argument” famously defended by Jackson when he was still a dualist.)  The basic idea of the straw man is that dualists (so the story goes) posit the existence of a kind of “stuff” that is not a material kind of stuff insofar as it is intangible, invisible, tasteless, odorless, etc., but which is nevertheless in other respects somewhat like a material thing in that it is made up of components (albeit non-physical ones) which are causally related in various ways, instantiates mental properties in something like the way the materialist thinks the brain instantiates them (only without being material), and so on.  This purported “ectoplasmic” “stuff” is, in other words, thought of as a kind of non-material substrate in which mental attributes inhere or a non-material container in which they are placed.  The materialist then asks why positing a non-material stuff, substrate, or container is any more helpful than positing a material stuff, substrate, or container.  For wouldn’t the arguments that the dualist says show that mental attributes can come apart from the latter also show that mental attributes can come apart from the former?

As I have noted before, the problem is that this is precisely not what any prominent dualist philosopher thinks the mind is, and no one who has carefully read what thinkers of the past like Aquinas, Descartes, Leibniz et al. and the contemporary writers influenced by them have actually written could suppose that it is. 

Descartes, for example, does not think that the res cogitans is a kind of “stuff” or container or substrate in which mental properties inhere and which could intelligibly exist apart from them.  He doesn’t think that the mind has thought.  He thinks that the mind is thought.  That is its very essence, that without which it could not be.  He is concerned precisely to deny that there is any metaphysical daylight whatsoever between the res cogitans on the one hand, and thought on the other, by which the one could intelligibly be said to exist apart from the other.  He thinks that the mind is in this sense a simple rather than a composite substance, i.e. rather than something made of parts that could come apart.  Accordingly, it simply misses his point entirely to suggest that the res cogitans is “made of” anything (“ectoplasm” or otherwise), that it might exist without “instantiating” its mental attributes, etc.

Of course, one might raise various questions and objections to all this.  But the point is that until one understands what Descartes is actually saying, one has not even engaged with him much less refuted him.  And the same thing is true of dualists influenced by Descartes, from Leibniz to Popper to contemporary Cartesians. 

Aquinas and other Scholastic thinkers who regard the intellect as incorporeal also hold to the simplicity of the soul (though of course the way they would spell this out would differ given the difference between Scholastic and rationalist conceptions of substance, essence, etc.).  In yet other ways too the position defended by Thomists and other Scholastic writers is simply nothing remotely like the straw man attacked under the “ectoplasm” label. 

For example (and as I discussed in an earlier post) for Aristotelian-Thomistic philosophy, the divide between the material and the immaterial is not all-or-nothing and it does not essentially have to do with what kind of “stuff” a thing is made out of.  Matter, in Aristotelian-Thomistic thinking, is essentially that which ties form (which is otherwise universal) down to a particular thing, time, and place; it is that which accounts for a thing’s changeability and imperfection; and so on.  Matter qua matter thus corresponds to potentiality, particularity, multiplicity, changeability, and imperfection.  Since these characteristics are susceptible of degrees, there is a sense in which materiality and immateriality can come in degrees.  The more something exhibits potentiality, particularity, multiplicity, changeability, and/or imperfection, the more matter-like it is.  The more something exhibits actuality, universality, unity, permanence, and/or perfection, the more immaterial it is. 

In this connection, it is interesting that Jackson and materialists in general tend, despite their materialism, to take realism about universals and other abstract objects more seriously than they do dualism.  For example, no one seems to think it a good response to such realism to characterize abstract objects as made of “ectoplasm” or the like.  It seems clear enough to all sides that this would be a silly objection aimed at a caricature.  In classical (Platonic, Aristotelian, and Scholastic) philosophy, however, the ontological status of universals and the immateriality of the intellect are very closely connected topics.  For Aristotle and Aquinas, for example, to have an intellect essentially just is to be capable of taking on a form without the particularizing features associated with specific individual things that have the form.  It isn’t a question of the form coming to be instantiated in some mysterious ectoplasmic kind of stuff, because it isn’t a question of its being instantiated at all, in any kind of stuff. 

Of course, the contemporary philosopher will find it hard to understand what is going on in such accounts if it isn’t a question of what sort of “stuff” the mind is “made of,” but that’s precisely the point.  The conceptual universe inhabited by older writers is very different from that taken for granted by contemporary academic philosophers, and the latter have a regrettable tendency to read their own basic assumptions back into older writers rather than taking the trouble to try to understanding the latter in their own terms.

Anyway, in fairness, this does take us far beyond anything Popper was committed to.  And there is in any case other and more interesting stuff in Jackson’s essay, to which I refer the interested reader.  One thing that is surprisingly missing, however, is any discussion of what I take to be Popper’s most interesting argument against materialism, to the effect that there can in principle be no causal account of the intentionality of language and thought.  I discuss this argument in my paper “Hayek, Popper, and the Causal Theory of the Mind,” which is reprinted in Neo-Scholastic Essays.

Related posts:

Popper contra computationalism

Popper’s World 3

Bühler? Bühler? [Popper on the four functions of language]

Some brief arguments for dualism, Part V [On one of Popper’s anti-materialist arguments]

When Frank jilted Mary [On Jackson’s “knowledge argument”]