Wednesday, April 19, 2006

Eliminative Materialism and Neuroscientific Successors

BDK wrote:
To lie is to know X is false, but to assert X anyway. The EM advocate would just say that knowledge is a property of internal nonpropositional representational states that can be true or false, or if you prefer, can provide a better or worse fit to the world. This, of course, is the positive story Churchland has been developing with his state space semantics, or recently he's been calling it 'domain portrayal' semantics.

VR: OK so you can have a nonpropositional representational case that a proposition is false? I'm sorry, but that sounds like burning water, military intelligence, jumbo shrimp and compassionate conservatism. If I am in a state that can be true or false, that state is to all intents and purposes a propositional attitude.

BDK: Victor, you keep giving indirect arguments. What about the contents of your visual experience: are they propositional?

VR: I can see something without having any propositional thoughts. But my visual experience invariably gives rise to propositional thoughts.

BDK: 2) They are nonpropositional. In this case, what is to be feared if all contents are nonpropositional in a similar way? Our visual experience is extremely rich, much more thick and nuanced than can be described in a few words. Perhaps most of our brain uses a similar high-capacity, parallel, nonpropositional representational format, and linguistic tokens are anemic reflections of such rich internal contents.

VR: At the end of the day, I am trying to account for my own experience. And I am aware of all sorts of propositional thoughts. I am aware of the meaning of the sentence I just wrote. I am aware of what I mean when I am presented with a definition of eliminative materialism. Not every part of my mental life is propositional but by golly a lot of it is, especially my entire career as a blogger.

What the Churchlands do is say that they are replacing propositional attitudes with something that they describe in non-propositional terms that fits more nicely with what a brain scientists sees (or the ultimate brain scientist will see) when you look at the brain. Then when you ask them how what is going on has anything to do with knowledge as you know and understand it, and they then tell you that, well, of course this neuroscientific description is what knowledge really is, and that you shouldn't worry about what is going to happen to knowledge, or the distincition between telling the truth and lying, or what have you. It all seems like double-talk to me.

Lynne Baker writes: Throughout, he conflates views on the nature of knowledge and views on the mechanisms that encode it.
Connectionism, if true, may falsify sentences-in-the-brain models of internal mechanisms, but all that would follow is that propositions and propositional attitudes should not be understood in terms ofsentences-in-the-brain. Throughout, the (plausible) claim that if connectionism is true, then sentences-in-the-brain models are false is elided with the distinct (and implausible) claim that if connectionism is true, then knowledge is nonpropositional. [This footnote is taken from my review of Churchland's A Neurocomputational Perspective. The review appeared in The Philosophical Review 101 (1992):906-908.]


Blue Devil Knight said...

You are right that truth and the like hasn't been a focus for the EMers from the get-go. They have spent a lot of time on more basic questions about the dynamics of neural nets and the like, without thinking as much about normative issues. This would have been a great criticism about ten years ago.

But as I've said a couple of times now, they do think brains construct models of the world, and these models can be closer or further from reality.

For example, I think the contents of my visual experience are a model of the world (a nonpropositional model of what is happening in the "specious present" to evoke activity in my retinae). This model can be inaccurate (illusions) or accurate (we are very good at determining if two lines are parallel). What does this concept of a model's fit to the world leave out that you want with truth?

I do not experience propositional contents directly, or if I do, I don't know they are propositional. I engage in verbal imagery, imagining myself or others saying things. I often have a feeling of understanding when I engage this sensory imagery. I sometimes have no such feeling of understanding, as when I listen to someone speaking in Portugese.

That feeling of understanding may indicate that there are propositional contents which I have (unconsciously?) "grasped". I prefer to stay neutral: I have an understanding of the statements, and frankly don't make confident psychological claims about the basis of my understanding. I am an agnostic. EMers are atheists. Propositional devotees are theists.

Blue Devil Knight said...

Incidentally, the neurophilosopher who has done the most work, to my knowledge, on this topic, is Rick Grush. The paper where he lays it all out is here.

I think he is doing the best work out there. Period. I look forward to his books coming out. He is technically proficient, but shows a sensitivity to truly philosophical issues that is unusual amongst the naturalistic types. I predict his name will become well known in philosophy, for good reason.

Victor Reppert said...

I'm not at all sure that the Churchland's position amounts to much more than a demand for open-mindedness until the science is done. They actually predict how the science will go, but this is in advance of the science actually being done, so it's little more than a prediction of the course of future science, which is always tough to do.