RE: SUO: On the (existence of the) supreme supertype
Adam Pease <apease@ks.teknowledge.com>:
>Pat,
> You state that causality should be prohibited from "unreal" to
>"real" and vice versa. Although I can see that the unreal-to-real
>case should be prohibited, I don't think the other direction should
>be strictly insulated. For example, it might make sense to assert
>information about "Adam's younger brother" (which doesn't exist) in
>an "unreal" world (or context), but if there is no Adam in the real
>world there is an effect on the unreal world which is that extra
>content (the existence of Adam) is required to be in the unreal
>world.
I see what you mean, but I would say that this is best described by
putting the real you (or maybe a facsimile or counterpart of the real
you) into the imaginary world as well as in the real one. A causal
influence between worlds (in any direction) would be something more
like a ghostly visitation or a paranormal event in the world where
the caused thing happened, since that would be an effect from a cause
in another world.
I suspect we agree on this, and I just didnt explain myself adequately before ?
Pat
> This is a pretty esoteric quibble though and I agree with your main point.
>
>Adam
>
>At 10:36 AM 2/22/2001 -0600, pat hayes wrote:
>
>>Phil, I won't say anything else about what we call T, but you do
>>raise an important issue, which can be summarized as the question
>>of whether existence should be a predicate. There is a potential
>>mismatch between 'exists' meaning actual existence in the real
>>world and 'exists' used as a quantifier in the logic. If we want
>>our logic to be able to reason about circumstances which might
>>never actually obtain (as is often done in planning. by considering
>>alternative possible futures, then deciding to perform actions
>>which make some of them impossible; and as is also done in
>>counterfactual reasoning), then we have to allow into the domain of
>>quantification things which do not in fact exist in the first
>>sense, and also be able to contemplate things which do exist having
>>properties which they never in fact have. So just saying
>>(exists (?x)(= ?x a))
>>wouldnt be enough to assert that the thing called 'a' *really*
>>exists; to do that one would need to say something more about this
>>thing called 'a'. Exactly what more is an engineering question
>>which we need to address.
>>
>>A common strategy is to introduce 'imaginary entities' or
>>'possibilia' as a distinct category in the classification
>>heirarchy, but I would argue that this is a mistake, on several
>>grounds. First, any kind of thing might be possible: one can have
>>possible humans, possible events, possible worlds, etc.., so as a
>>category this cuts across the entire classification spectrum.
>>Second, it suggests that possible-but-unreal things are somehow
>>another category of real things, much as birds are a kind of
>>organism. This gives rise to many well-known concpetual puzzles and
>>paradoxes, all arising from a basic misunderstanding. (Quine in a
>>famous passage points out the error in going from 'it is possible
>>that someone could have been standing in the empty doorway' to
>>'there is a possible person standing in the empty doorway', by
>>asking *how many* possible but non-actual people every empty
>>doorway has to contain?) And third, it masks the important point
>>that these non-actual things almost always seem to be 'inside'
>>non-actual worlds, ie we talk about an alternative set of
>>circumstances or alternative possible worlds (in which, say, I had
>>a brother who I don't in fact have), rather than putting the
>>possible but non-actual things into this real world. And there is a
>>good reason for this: if the possible-but-non-actual things were in
>>fact actual, they would have real effects on the rest of the world.
>>One cannot just insert a thing into the world and expect everything
>>else to go on just as before; so one is forced into thinking about
>>a wider set of circumstances than just the immediate surroundings
>>of the imaginary thing. As we all know, one dead sparrow might have
>>all kinds of repercussions, so it is usually safest to provide an
>>alternative world for the sparrow to die in, and see what happens
>>there.
>>
>>I think that a general-purpose SUO needs to allow non-actual
>>entities - it cannot presume that the existential quantifier means
>>existence in the real world - but that just allowing them casually,
>>as it were, without some attention being given to their effects, is
>>a well-known recipe for conceptual muddle. I would suggest that any
>>nonreal thing needs to be thought of as enclosed within a non-real
>>causal bubble which is large enough to provide a causal 'horizon'
>>insulating any effects of the unreal thing from influencing any
>>events in the real world, or vice versa. The safest such bubble
>>would be an entire possible world, but we might allow somewhat
>>smaller sets of circumstances or 4-d enclosing space-times to play
>>the same role. Then the way to introduce 'possibilia' into the
>>ontology is to introduce these 'bubbles', and allow 'IsReal' as a
>>predicate on them (which asserts that that set of circumstances
>>does in fact obtain in the real world somewhere/when). Then a
>>possible-but-not-real person (eg my imaginary brother) is simply a
>>normal person who has the misfortune to only be enclosed inside
>>nonreal bubbles. This overall picture has no need for a special
>>category of 'possibilia', therefore, and it is meaningless to even
>>talk about possible-but-unreal things inside real worlds.
>>
>>Pat Hayes
>>---------------------------------------------------------------------
>>IHMC (850)434 8903 home
>>40 South Alcaniz St. (850)202 4416 office
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>
>-----------------
>Adam Pease
>Teknowledge
>(650) 424-0500 x571
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