Philosophy of Computer Science
Position Paper #3:
Is the Brain a Computer?
Last Update: 24 February 2010
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For this position paper, I would like you to evaluate the
following "complex" argument.
(It's "complex" because it consists of 3
"sub"arguments, two of which treat the conclusions of previous ones as
- Turing's Thesis:
A physical object can compute if and only if it can do what a (Universal) Turing
Machine (TM) can do.
- A computer is any physical device that can compute.
(Consider this as a (proposed) definition of ‘computer’.)
- The human brain is a physical object that can do what a
(Universal) TM can do.
- Therefore, the human brain is a computer.
- Microsoft Word is TM-computable. (I.e., a Universal TM can
execute Microsoft Word.)
- Therefore, any computer can execute Microsoft Word.
- Therefore, the human brain can execute Microsoft Word.
As usual, to evaluate this argument, you must determine whether
(I) it is valid
(II) all the premises are true.
If both of those conditions hold, then an argument is said to be sound.
You are logically obligated to believe the conclusions of sound arguments!
- So, if you ever come across an argument that you think is sound,
but whose conclusion you don't believe
(by the way, do you
really believe line 7 of this argument?), then either one or more of the
premises are false or it is invalid
[i.e., there is some way for the premises to
be true yet for the conclusion to be false].
To determine whether the argument is valid,
you must suppose (or make
believe) "for the sake of the
argument" that all the premises are true,
and then consider
whether the conclusions logically follow from them.
(Or: Can you imagine
some way the world might be so that the premises are true but the conclusion
Note that there are three conclusions: lines 4, 6, and 7.
you agree that conclusion 4 follows logically from premises 1–3,
that conclusion 6 follows logically from premise 5 (maybe with the help
of some of the earlier premises),
and/or that conclusion 7 follows
logically from lines 4 and 6 considered as premises?
If not, are there missing
premises that are needed to make the argument(s) valid?
If there are,
do you agree with them (why/why not)?
- It may be too difficult to determine whether each
premise is true or false.
More realistically, you should decide whether
you believe, or agree with, each premise,
and you must explain
why you do or don't.
Finally, do you agree with the conclusion(s)?
If you do, but you think
that there's something wrong with the argument, try to present a
If you don't agree with the conclusion(s), state why,
and try to give an argument for what you do believe.
Your position paper should be approximately
to lecture on the due date.
At the top of the first page, please put the following information in
the following format:
|Position Paper #3, Draft 1
||CSE 484 (or 584) (or PHI 584)|
For general assistance with writing (including my preferred method of
paper preparation and format, as well as advice on grammar),
website "How to Write".
As before, no
abstract is needed for this position paper, but you do need to give full
citations to any sources that you cite.
DUE AT THE BEGINNING OF LECTURE, MONDAY, MARCH 15
Copyright © 2010 by
William J. Rapaport