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From: tmoody@sjuvax.UUCP (T. Moody)
Newsgroups: net.philosophy
Subject: Machines
Message-ID: <2464@sjuvax.UUCP>
Date: Mon, 28-Oct-85 07:53:32 EST
Article-I.D.: sjuvax.2464
Posted: Mon Oct 28 07:53:32 1985
Date-Received: Sun, 3-Nov-85 10:18:18 EST
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Organization: St. Joseph's University, Phila. PA.
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[]
If we are going to spend any time discussing minds and machines, we
ought to take the time to reach a consensus on the meaning of
"machine".  This has already become problematic in the exchange
between Michael Ellis and Rich Rosen.

Rosen concedes, for "machine", what he has refused to concede for
"free will": that the term is inherently vague.  Astonishing as it is
that he should deny the vagueness of "free will" -- given that *its*
meaning has been the subject of dispute for centuries -- he is
certainly correct about "machine".  Philosophical interest in the
definition of "machine" is quite young, though.

The trouble is, I think, that the word "machine" is used both
literally and metaphorically in philosophical discussions (esp. about
the mind).  Literally, we all understand that machines are man-made
artifacts, devices, tools, and systems.  In this literal sense, no
living thing is a machine.

But this doesn't really help, because what we want to know is whether
any living things, or parts of living things are sufficiently *like*
machines, in essential respects, to justify the application of the
term to them.  Are cells, for example, "biological machines"?

In order to answer this question, we need to *abstract* from the
literal meaning of "machine" -- which clearly does *not* include cells
-- a more comprehensive meaning that captures what we think is
essential to machinehood.  For clarity (well, maybe), I shall refer to
machines in the latter sense as "Machines" (upper case "M").  It ought
to turn out that while all machines are Machines, not all Machines are
machines.

Proposed definition 1: A Machine is any deterministic system.  That
is, its current states are exhaustively determined by its prior
states.

Proposed definition 2: A Machine is any system whose behavior is
Turing-computable.  That is, its behavior can be completely specified
by some finite Turing Machine algorithm.

Now, I *think* these two definitions are coextensive...but I'd like to
know what you folks think.  Here is my reasoning: If a system is
deterministic, its behavior is completely described by laws
expressible as mathematical functions.  Granting the Church/Turing
thesis (anything computable is Turing-computable), these are
Turing-computable.

Okay.  Since quantum mechanics, it is no longer plausible to
characterize the universe itself as a Machine.  In fact, since quantum
mechanical systems are not Machines, we are forced to concede that
Machines are statistically emergent entities.  A digital computer, for
example, is a Machine (also a machine, of course), even though the
electronic events that animate it are subject to quantum mechanical
indeterminacies.  The computer is configured in such a way that these
indeterminacies are largely cancelled out, so that at a molar level of
description a digital computer is approximately deteministic.

Is the human brain like a digital computer in *these* respects?  Are
*its* indeterminacies approximately cancelled out, making it a
statistically emergent Machine?  This is, after all, an empirical
question.  Based on what I have read, the answer is no, but I think it
is fair to say that the case is not closed.  Note that not many
neuroscientists state any position on this question, because they are
not primarily interested in these metaphysical problems.  Sir John
Eccles (who is, interestingly, a strict dualist) argues that the
brain amplifies quantum indeterminacies, if anything.

Also note that this has nothing to do with the Searle argument.
Searle's point is that even if one grants the Machinehood of the
brain, that is not sufficient to establish its intentionality.


Todd Moody                 |  {allegra|astrovax|bpa|burdvax}!sjuvax!tmoody
Philosophy Department      |
St. Joseph's U.            |         "I couldn't fail to
Philadelphia, PA   19131   |          disagree with you less."