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Re: [ontolog-forum] Thing and Class

To: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Mon, 22 Sep 2008 12:04:41 -0500
Message-id: <E398F4C9-A587-4FBC-B03E-5DE5453F972C@xxxxxxx>

On Sep 22, 2008, at 7:48 AM, Matthew West wrote:

Dear Pat,
Sorry for the delay in replying. I am just back from a week’s holiday in Morroco.

Lucky you :-)

See responses below.
Matthew West
[MW] <snip>
then featherless biped will include (from history) T. Rex, and from
mythology those creatures with a goats hind legs and a human torso and head.
My argument would be that for anything that is not provably equivalent,
is at least some possible thing in some possible world that is a member of
one but not a member of the other.
That seems to be the key. Your stance, then, is that intensional differences will always be revealed as extensional differences in some possible world: and if we agree to quantify panoptically over all entities in all possible worlds, then it will be an extensional difference. Ergo, intensional differences ARE extensional differences, if one casts ones extensional net widely enough. Good point, though to be fair to the rest of the philosophers, they are usually referring to extensions in the actual world (maybe an eternalist one, but still without unicorns in it.)
[MW] Then they do not wish to be extensionalist. If you do, I think you have little choice but to quantify over possible worlds (which is a good thing, because it forces you down a single path and closes out many options).

I agree its a good thing, but you underestimate the stubbornness of philosophers. Many of them DO intend to be strictly extensionalist AND strictly realist. Nominalists in particular. I have to say, I have a strong sympathy with such a position. I don't for a second think that alternative worlds *really* exist, in fact I don't even believe that numbers exist in the same solid sense that, say, trees and buckets of oil exist. But I also agree with you that we need to quantify over them, i.e. talk as though they exist, in order to get practical ontology (and arithmetic) done. And I'm quite happy to live in this schizophrenic state where my actual philosophical position is different from my practical ontology engineering position. 


What you say is very "natural" for someone with a background in logic
and traditional set theory which has a strong emphasis on predicates
equating to sets or types, but this is not an inevitable choice.
Of course, but that is the point. Extensionality *is* the decision to
identify predicates with sets.

[MW] Perhaps I am not clear enough. My objection is having to accept
something set like whose membership can change with time. It may be my 
error to conflate that with intensionality.
I think it is, yes. Personally I have no objection to set-LIKE things which are dynamic: after all, everyday collections like flocks of sheep seem to have this character. But my point was that to call these sets is simply an error. 
[MW] We have tried quite hard to eliminate anything that is not a set. The one thing we have noticed that are set-like but not strict sets, are what are often called ordered sets, e.g. the set of temperatures. The problem here is that the same strict set may have more than one ordering.

Hmm. Why are you concerned to eliminate all but sets? Surely most of the universe is populated by things that aren't sets. I don't see ordered sets as posing any kind of "problem". In fact, if anything, ordered sets - sequences or tuples - are more use in everyday ontologizing than unordered sets. 

[MW] <snip>

Bottom Line
There are a number of ontological positions that you need to choose
between, and it seems to me that we have not made all the same
and this is what is resulting in the differences we have found here.
The key choices that seem to me to be relevant here are:
1. Do particulars have temporal parts or not.
i.e. are particulars extended in time as well as space (or not)?
Physical (spatiotemporal) particulars. The number 7 is a particular
but isn't spatiotemporal.  Here's another way to say it: can something
occupy space without occupying time? Yes (continuants) or no ("4-d")?

[MW] Yes. At present ISO 15926 treats numbers as classes, and I appreciate
that is not the only, and may not be the best approach.

Hmm. I would prefer to treat numbers as numbers, myself. 
[MW] Indeed, the question though is what sort of thing is a number?

Why do you need to answer that question? For that matter, why do you need to ask it? But if you insist, a number is a platonic abstract entity, not a spatiotemporal one. 

You seem to be saying it is a particular, and in this way like a spatio-temporal extent.

Whoa. I certainly wouldn't make that identification. There are many particulars that aren't spatiotemporal (possible worlds, for example :-)

I don’t see that similarity.

Nor I.

For me the key separation is between spatio-temporal extents and everything else, which I call Abstract Object. Then sets, ordered sets and numbers would be subtypes of this.

Yes, what I called 'platonic' above. Quite, we seem to agree. (Not that classifying a number as an abstract object is exactly rocket science :-)

However, I appreciate that there is an arbitrariness about the choices at this level of abstraction. What is your rationale for making numbers particulars?

I take 'particular' as simply meaning the opposite of 'universal'. So numbers, like 37, are particulars. 

2. Extensionalism (or not) in particulars.
i.e. if particulars coincide, are they the same thing?
Do you mean spatiotemporally coincide? Like a bottle and the glass it
is made of?

[MW] Yes, but the bottle and the glass it is made of will only coincide
accidentally. The usual case is that the temporal extent of the glass
is greater than the temporal extent of the bottle, and indeed the bottle
is a state of the glass. This also means that bottle is not a
subtype of glass-object (the whole of its life), but state-of-glass-object
Its not hard to imagine a scenario in which the thing and the piece of stuff exactly coincide in 4-d. Consider for example a bottle made of some heat-formed polymer, which is made by blowing a gas into a hot mold, and comes into existence in the form of a bottle; and then ends its life by being incinerated in a flash furnace. Here the bottle and the piece of stuff of which it is made occupy the exact same 4-d history, but some folk would still want to distinguish them. For example, someone might want to assert a property of one but not the other. I agree its much less plausible to want to make the distinction in cases like this, but I can see a pragmatic reason for doing so, which is that we make the distinction in the more usual cases, perhaps for good extensionalist reasons, so why should we be forced to not make it here? 

[MW] This is just the price of extensionalism. Your only alternative is to say that sometimes two different things occupy the same spatio-temporal extension. Once you admit exceptions, the slope is very slippery.

I don't see there being a slope here. Suppose we were to simply toss extensionalism aside, and allow that two different things might occupy the same exact history. (There might be a kind of weaker extensionality saying that this is impossible for two entities of the same 'kind', eg two pieces of stuff, but lets ignore such complications for now.)  What would break? What conclusions would then fail, that you wish would not fail, or follow that you don't want to follow? Put another way, what actual ontological use is the extensionality assumption?

As I say, I have yet to find a case where it actually mattered (and I have been looking for them for many years now). I would be very interested in any difficult examples you could produce that challenged that position.
3. Eternalism vs presentism.
i.e. is everything that exists what exists now, or is everything that
exists include all that exists in the past and the future?
Also possibilism: even hypothetical things exist. But this 'exists'
has to be taken with a pinch of salt, or at least clarified, as it
really doesn't mean what people ordinarily mean when they talk about
the world in English. We say things like, "The hadron supercollider
didn't exist in the sixteenth century."  I suggest a better (less
confusing and contentious) way to say it is, the logic admits all
possible, future and past entities in its universe: they all
*logically exist*. But only a small fraction of the things that
*logically exist* ACTUALLY exist (i.e. in the actual world, now). So
actual existence is a predicate (or a type, if you like) in the
logical description. To 'logically exist' simply means that it is a
thing that can be referred to, can be discussed, can be given a name.
So this is really only another way to say that all names refer, which
is the basic semantic assumption of logic.

[MW] Well I'm nearly with you here. For me actually exist means everything
in our universe, for all time, and not restricted to now. That would be 
a further restriction.
Speaking like an ontologist, I agree. But when you aren't doing ontology, do you really talk this way? Would you say that Julius Caesar exists, in the same sense that (unfortunately) Sarah Palin does?
[MW] I am quite happy to talk 3D as well as 4D. However, when I want to integrate different views of the world, it is ALWAYS a 4D view that I integrate into.

I would like to be a fly on your shoulder for a few hours, and then whisper back to you all the times you used 3-d talk and 3-d assumptions without remarking on it , or maybe even noticing. It really does seem to be almost welded into English discourse, probably because English - all NL - evolved in a situation where people were using it to communicate in a 'present', and we are all inherently conscious in a 'moving present' , even though that idea is incoherent. 
Now my choices are:
- Temporal Parts
- Extensionalism for particulars
- eternalism
- Extensionalism in sets
I agree except for the second. Don't you want to be able to
distinguish the bottle from the glass out of which it is made? Or have
I misunderstood what you mean by this?

[MW] No you have not misunderstood, but I can distinguish between the 
bottle and the glass (see above) and when I can't it does not matter,
because any statements I would make about it as one would also be true 
of it as the other.
An intensionalist is going to say: but it may be true to say of the bottle that it could have been made of polythene; but it is nonsense to say that a piece of glass could have been made of polythene. I know how you will get past this objection, but it illustrates that you have to be careful when you say 'any statement'. 
[MW] Of course, possible worlds again (it gives you a lot of mileage once you have paid the price).

Oh, I agree entirely. 

But this is philosophical debate, and IMO somewhat irrelevant for Working Ontology :-)
[MW] Now here I completely disagree. I think that a rigorous and well defined set of philosophical ontology commitments are critical to practical working ontologies. If you do not make you commitments explicit, then different workers on the ontology cannot be expected to conform to them, and then you will have different commitments in different parts of your ontology. Also, the more rigorous our ontology philosophically, the simpler it  is going to be, and that has processing implications as well.

I agree about the commitments. BUt philosophers will argue about whether or not those commitments are correct. Thats where philosophy parts company with ontology engineering. 

I actually think that it is a great shame that philosophical choices and their practical consequences are not discussed a great deal more in this forum.

Practical consequences, exactly. Philosophers, by and large, as a species, do not take these very seriously when actually doing philosophy. We need a new name for just the right amount of philosophy, but not actual full-blown academic philosophy as practiced by philosophers. 


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