Saturday, October 22, 2005

I don't make empty threats

In my last post, I threatened to analyze John DePoe's paper, "An Argument Why the Mind is Not a Physical Mechanism." Well, here goes.

First, let me discuss his dismissal of physicalism. The basic argument, as I understand it, is that in a physicalist universe, rational thought and purposive action are not possible. What does he mean by purposive action? Consider a thermostat. It acts to keep a room at a constant temperature. Isn't that purposive? It can be explained by purely physical means. Does he mean consciously purposive actions? Okay, would you agree that a computer is not conscious, even a cutting-edge one? Ever played chess against one? Before computers, the ability to play chess was considered indisputable evidence of consciousness. A computer chess algorithm is purely physical, but can seem purposive. I have seen my computer sacrifice it's queen for a winning position. That seems pretty purposive. Let's look at the difference between a human brain and a computer CPU, in terms of intraconnectivity (yes, that is correct, intraconnectivity). A Pentium 4, 3.0Ghz processor has 125 million transistors. Each transistor has 3 connections (Gate, Source, Drain) to connect it with other transistors. A human brain has billions of neurons, each with thousands of dendrites connecting it to other neurons. Even without doing the math, it is pretty obvious that the human brain is several orders of magnitude more complex than a computer. So if physical causes can seem purposive in a computer, how much more purposive would be physical causes in a human brain? Notice that physicalism states that ultimate physical causes must be present. In the philosophy of consciousness this is called "supervenience." A simple causative path is not necessary. Mr. DePoe's dismissal of physicalism in not well founded.

I actually agree with his argument against global external justification.

In my last post I showed that his use of Bayes' Theorem is nonsense. But after reading it again (and again), I found more reasons for this beyond the misuse discussed in the last post. Let's look at his variables: R, N, E, and C.
R - human cognitive faculties are reliable.
N - metaphysical naturalism - this means that no supernatural (non-physical) forces exist.
E - Humans have cognitive facilities (that is: minds) that have arisen through evolution.
C - Humans have blah, blah, blah. He means humans have minds.
Now, he says that the probability of R, P(R), is near one. That's debatable, but I'll go with it.
P(x|y) means the probability of x happening given that y has happened.
so: P(N & E & C | R) =P(N & E & C), since P(R) is assumed to be 1, and so will have occurred in all trials.
P(N & E & C) = P(N) & P(E) & P(C)

P(N) - the probability that nothing supernatural exists - He is trying to argue that 'mind' is non-physical (supernatural) and therefore P(N) = 0, so using this in any equation to support his argument reduces that equation to triviality (0=0, no information)

P(E) - the probability that mind arose through natural selection - Again, he is trying to demonstrate that P(E) = 0. Same argument as above.

P(C) - the probability that humans have minds - Humans do have minds. P(C) = 1. since P(x&1) = P(x), this drops out of the equation.

My conclusion: Mr. DePoe seems to have a poor grasp of probability, and has in no way shown that evolution (or rather natural selection) could not have produced the human mind.

He also restates the purposive causation argument that he used to dismiss physicalism. The same reasoning applies. He hasn't shown that physicalism (above) and natural selection (here) can be dismissed.

"Since mental sensations can cause something physical to occur (e.g., my utterances about beliefs that I have about mental sensations), epiphenomenalism is false."

Epiphenomenalism - physical causes can have mental effects, but mental causes cannot have physical effects.

My answer:
Supervenience - all mental causes are themselves effects of physical causes.
See Jaegwon Kim, "Physicalism, or Something Near Enough," Princeton University Press, 2005.

As for Mr. DePoe's argument against agent causation. Agent causation itself seems incompatible with physicalism, and I can't see how this argument in any way shows that the mind cannot be a purely physical phenomenon.

I do not think this paper achieves it's purpose.

I'd like to make one last comment on this paper.

Obfuscation - a big and confusing word that means big and confusing. Generally considered to be an extremely poor writing technique.

Later,

1 person has spouted off:

jackal said...

By saying P(N) and P(E) = 0, he's just assuming his conclusion. Am I wrong?