Jim Clark wrote:
> There is often a confusion between the in-principle explanation
> of macro phenomena by reductionist mechanisms and the
> implications for actual prediction. A leaf falling from a tree
> is a prime example. The physicist would have a terrible time
> predicting the path of the leaf with any accuracy, but that does
> not mean that we need anything more than the physical processes
> to explain its path.
This is discussed in some depth by Jerry Fodor in the forward to "The
Language of Thought" (a piece previously published as "the special sciences
paper"). However, I believe that the confusion is actually between the
in-principle ontological "reduction" of phenomena to physics (on the one
hand) and implications for both prediction AND explanation. Fodor uses as
his example a particular law of economics ("Gresham's Law", if I remember
correctly), which makes statements about phenomena described as "monetary
exchanges". Surely each example of a "monetary exchange" is a physical
event. Just as surely, it is not possible to specify in advance which
physical events constitute "monetary exchanges" and which do not. The
phenomena covered in that economic law are physical phenomena, but cannot be
predicted OR explained by reference to their purely physical descriptions.
G. Marc Turner wrote:
> Just thinking about reducing "mental events" down to physical
activities...
> so, one day in order to test someone's knowledge of an area all we will
> have to do is measure some physical activity (e.g., firing patterns
between
> a few neurons when presented with a certain question).
One need not believe in "souls" or nonphysical "minds" to understand why
this is unlikely. My belief that the sun is shining is a physical
phenomenon, instantiated by a particular pattern of neural activity. But
there is no reason to believe that particular pattern is in any sense "the
same" as the patterns instantiating any of the following:
- Your belief that the sun is shining.
- My cat's belief that the sun is shining.
- My belief yesterday that the sun was shining yesterday.
(etc.)
Suppose that we were to postulate a simple psychological law which states
that
If a person believes that the sun is shining, that person will not carry an
umbrella.
Both halves of that law (a person's belief that the sun is shining, and
"carrying an umbrella") are physical events. But each half can only be
described physically if one is willing to use infinite disjunctions of the
nature of
X believes the sun is shining if X has neural pattern A or if X has neural
pattern B or if X has neural pattern C ...
X is carrying an umbrella if X has an object of type U in his left hand, or
if X has an object of type U in his right hand or ...
In short, even such a simple psychological law cannot be understood in
purely physical terms, nor can the physical descriptions of the covered
events be used to make useful predictions. But just as surely there is no
need to make up non-physical events or entities (which of course explain
nothing anyway - they're really just dodges).
I find this completely satisfying. Ontologically, everything reduces to
physics. But explanations and predictions do not. As Fodor concludes, no
matter how advanced our physiology and biology and chemistry and physics
become, we will always need psychology and sociology and economics.
================
Incidentally, I said that I find the idea of brain scanning for learning to
be "unlikely", not "impossible". I'm sorely tempted to say "impossible", but
I've learned that when one says that, it's a sure signal that within a year
or two someone will develop a way to do it. On the other hand, I'll say with
complete confidence that we will not eventually discover a nonphysical
"mind" or "soul". Feel free to hold me to that one. :)
Paul Smith
Alverno College
Milwaukee
