Wednesday, August 29, 2007

Doctor Logic on modeling

Doctor Logic apparently wants to explain intentionality and the ability to understand it, in terms of modeling.

I think we need to get a whole lot clearer on what we mean by modeling. It seems a mistake to explain meaning in terms of modeling, since as I understand modeling, it somehow has to have meaning already.

There are two things I look for when I see a naturalistic account of any of the phenomena required for reason. First, I look to see whether the description is really physicalistically acceptable. Is it really skyhook-free, or does it slip the skyhook in through the back door, use the word "brain" to make it sound naturalistic, and call it good. Carrier's account of intentionality reeks of this kind of procedure, as does Dennett's attempt to explain intentionality in terms of the intentional stance.

The other is to see whether the rational phenomena are recognizable when we get through. Does it really look like consciousness, or reason, or normativity has really been explained, or has it simply been explained away and replaced with a lot of scientific talk. Sometimes we are honestly told that we are being presented with an error theory: that what we thought was going on when we reason really isn't. I take it that is what it means to be an eliminativist about some dimension of folk psychology.

I wondering if Doctor Logic has Dennett's account in mind here, from Darwin's Dangerous Idea.

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At 8/29/2007 03:20:00 PM , Anonymous Anonymous said...

Dr. Reppert,

I have learned much from you and your book. As a Christian theist studying graduate philosophy, I am thankful for you and Plantinga "paving the way" for guys like me.

Is there an email address on your webpage that I may send you my "Epistemic Trigger Argument"?

In Christ,


At 8/29/2007 06:38:00 PM , Blogger Blue Devil Knight said...

On the brain constructing internal models of the world, from a philosophical perspective Grush's work is the best, such as this paper. At this point it is a pretty well established research program in motor control with quite a bit of evidence in support.

Whether sensory systems work the same way is very much an open question.

At 8/29/2007 08:50:00 PM , Blogger Victor Reppert said...

Keith: My page on the Glendale Community College web page has my e-mail address on it.

At 8/30/2007 02:11:00 PM , Blogger Doctor Logic said...


I'm not thinking about it in terms of any particular model, though I often imagine the brain working using the sorts of hierarchical temporal memories described by Jeff Hawkins.

Maybe I can give you a general idea of where I'm coming from. I think that one can make a good case that the mind operates on certain principles of recognition, pattern matching, generalization, prediction and so on. Dogs do not possess all these mechanisms at the same capacity, whereas humans do.

There's nothing magical required by any of these functions. Auto-associative neural nets can do it all.

Here's a flavor for the details. If I see an apple, the image of that apple feeds into my brain. Networks in the brain learn this signal, and can play the signal back on the mind's eye (which uses the same circuitry in the visual cortex). In fact it can play the signal back in a general way, scale invariant and location invariant. (Auto-associative nets can do this.)

Such networks are content addressable. If I see a part of an apple, it triggers the memory of the whole apple, and the image of the apple in the visual cortex is completed by the memory.

My later thought of an apple (in the absence of sensory stimulation) is "about" that external thing that would register on my visual cortex in the same way as the thought, or, perhaps, "about" that set of stimuli that would trigger the memory of the apple.

I think that this mechanism can be generalized to handle all instances of "aboutness".

For example, the concept of an apple goes beyond 2-D visuals to 3-D visuals, and taste, and smell, and weight, etc. A thought about a real apple is about the things that register in the same way on the respective sensory areas of the brain that formed the apple concept in the first place.

If I compose two thoughts, e.g., "an apple" and "the hood of my car" to form "an apple on the hood of my car", I am painting a picture on the very regions of the brain that would trigger if I were to see those items. That constellation of thoughts is "about" the sensations that would trigger the same constellation of thoughts.

There are also regions of the brain that are introspective, and that makes it possible to have thoughts about thoughts.

This is no error theory. See any skyhooks?


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