Dear Pat,
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,
there
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.
[MW] Yes, I was talking to one yesterday (Peter Simons). He
asked after you. I am sympathetic to such scruples if I put a purely
philosophical hat on, but once I am in engineering mode, I set them aside.
Utility is then king.
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.
[MW] A position we seem to share.
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.
[MW] Sorry, I was assuming too much context. I meant that we
tried quite hard to eliminate all abstract objects (i.e. not spatio-temporal
extents) except sets. This is just a search for parsimony, not a holy crusade.
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] The only problem we had was that we hadn’t taken
sufficient account of them. Although I was not really thinking of (arbitrary) tuples
when I was talking of ordered sets, but sets for which there is at least one
(and possibly more) ordering function, such as real numbers, and temperatures.
The issue is that it is the combination of set plus ordering function that is
what you are after, and not just the set. But this is not difficult once you
have worked that out.
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.
[MW] That is how I would treat them now, as abstract
objects, but not a set.
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.
[MW] I meant like rather than being one. But you have been clear
above on this, and that is fine.
There are many particulars that aren't spatiotemporal
(possible worlds, for example :-)
[MW] Ah! Now possible worlds I do see as spatio-temporal. I have
any possible universe as a possible spatio-temporal extent, and has other
possible spatio-temporal extents as parts. They are just not spatio-temporal
parts of this universe we inhabit (and are quite possibly not “real”).
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.
[MW] I take it you mean universals to be things that have
members (e.g. sets) and particulars to be things that do not have members, and
this would indeed be something that spatio-temporal extents and numbers would
have in common.
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
[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.
[MW] I find it hard to think of an example. It seems to me that
anything true of one would necessarily be true of 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?
[MW] The question would be, just which classes cannot share the
same spatio-temporal extent, and a duplicate must be produced. Of course you
could go all the way here, and say that a spatio-temporal extent can only be a
member of one class, and that you have as many as you need to support that. But
that is rather unattractive. For example I might then have three spatio-temporal
extents that are identical, one is a piece of metal, another is a car, the
third is red, but what I really wanted was a red car made of metal.
Sorry, I really prefer the simplicity of spatio-temporal
extensionalism, at least until some cases turn up that are too painful to
continue with it. (see challenge immediately below).
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.
[MW] If you had done that exercise 10 years ago, you would have had
an amusing time and I a confusing one, but these days, when thinking
analytically, I would consider it unusual to slip into 3D thinking, even though
I might use 3D language on occasion.
- Extensionalism for particulars
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.
[MW] Yes, I think the cross-over is that looking at it
philosophically helps you to try to minimise your commitments (which is a good
thing) and also of knowing the price of the commitments you have made (rather
like your excellent discourse on FOL the other day).
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.
[MW] I have suggested applied philosophy a couple of times,
without attracting too much heat. I would certainly consider this to be
my approach to philosophy.
Regards
Matthew West
http://www.matthew-west.org.uk/
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