[FOM] Possible worlds

[Eray Ozkural]

Some quick comments in the interest of the list

On 12/20/06, Timothy Y. Chow <tchow at alum.mit.edu> wrote:
>   "There might be life on Mars"
>
> ---a statement that is presumably either true or false but we just don't
> know which.  But isn't there another point of view (an intuitionist view?)
> under which "FLT might be false" is more analogous to
>
>   "The international community might send a manned mission to Mars in
>    the next 50 years"
>
> ---which seems to involve a different sense of possibility, one that
> doesn't seem to be "just" a matter of epistemology?

Tim, there doesn't seem to be any deep difference between
the two statements, namely because there will either be a manned
mission to Mars in the next 50 years, or not. Under this interpretation
both statements invoke with the ordinary and "sane" sense of
possibility. In other words, with epistemic possibility which deals
with how the world may be:
http://en.wikipedia.org/wiki/Epistemic_possibility

(This is also what probability theory deals with, and should be sufficient
for most discussions of possibility.)

However, if you looked for a statement analogous to "FLT might be
false", then this would in fact be a subjunctive possibility:
http://en.wikipedia.org/wiki/Nomological_possibility

An example for that would be:
"The Pope might be a woman"
and this sentence contains the stronger sense of "might" as opposed to
epistemic possibility in your above example.

The Wikipedia article is pretty decent and it decomposes subjunctive
possibility into four: logical, metaphysical, nomological and temporal
possibility.
Nomological possibility is "possibility under the actual laws of nature.",
I think you already know the others.

Particularist philosophers like me may choose to only talk about
nomological possibility so we may refuse thought experiments about
worlds that are _physically_ impossible. However, if one wants to consider
a world in which FLT is false, then one would have to invoke metaphysical
possibility. For this is in my opinion akin to saying "Water is NOT H20" (which
is the example in the wikipedia article, and also the subject of Putnam's
Twin Earth thought experiment). Yet other philosophers might take it as a
case of logical possibility. (I am not very certain, though)

Regards,

-- 
Eray Ozkural, PhD candidate.  Comp. Sci. Dept., Bilkent University, Ankara