[comp.ai] Free Will & Mcdermott's argument

planting@speedy.cs.wisc.edu (W. Harry Plantinga) (05/05/88)

In article <28437@yale-celray.yale.UUCP> dvm@yale.UUCP (Drew Mcdermott) writes:

>. . . any system that is sophisticated enough to model situations that its own
>physical realization takes part in must flag the symbol describing that
>realization as a singularity with respect to causality.  
> . . . robots with this kind of structure simply can't help but think of
>themselves as immune from causality in this sense.  
>Even after a reasoner has become sophisticated about physical
>causality, his model of situations involving himself continue to have this
>feature.  That's why the idea of free will is so compelling.   
>I would rather not phrase the conclusion as "People don't really have
>free will," but rather as "Free will has turned out to be possession of
>this kind of causal modeler."  So people and some mammals really do have
>free will.  It's just not as mysterious as one might think.
>
>                       -- Drew McDermott

Taking this as an argument that people don't have free will in the
common sense, let's see what we have.  Is this a fair restatement
of the argument?

    (1)  Systems that reason about causality and that reason about
    themselves have a singularity.  They must consider themselves
    exempt from causality.

    (2)  Therefore people are subject to causality and do not have
    free will (in the common sense).

As it stands, this is not a sound argument.  Clearly there are a couple
of unwritten assumtions here.  Perhaps these:

    (1.1)  People are "systems that reason about causality" (assuming
    materialism)

    (1.2)  The feeling of free will is the same thing as the feeling
    of not being able to reason about causality with respect to self.

If we accept (1), (1.1), and (1.2) we still can't conclude that people
don't have free will.  The best result that can be argued is

    (2')  If people didn't have free will, they would still feel that
    they did.

Note that this is very much distinct from (2), and even this argument
is based on some highly disputable premisses.  (1.1) is surely not
commonly agreed upon outside of AI, and (1.2) is also dubious.  My free
will doesn't feel like the simple inability to figure out what I am
going to do in the future by reasoning about causality.  My free will
feels like the ability to choose among alternatives no matter what my
reason, emotion, conscience etc. say is more "reasonable."

As an argument that people don't have free will in the common sense,
this would only be convincing to someone who holds (1.1) and (1.2) and
that (2') implies (2), i.e. someone who already thinks people don't
have free will.


Harry Plantinga
planting@cs.wisc.edu