Hi Pat, (01)
I am not sure what your point is here. (02)
Are you claiming that in the tradition that gave rise to the term 4d (in
modern times, Russell, Smart, Quine and Lewis) there was not an explanation
of the position in terms of the unreality of change and/or time? (03)
I find this strange. Quine, for example, makes a specific reference to
Parmenides. (04)
If you are arguing that you have a sense for changes in which these exist in
4d, then this does not seem to me to argue against my point. (05)
If you are arguing that this sense is the obvious natural language sense,
then there are lots of people who will disagree with you. I'll leave them to
it. (06)
If you want to claim that 4d has a nice way of explaining what we in natural
language talk about as changes, then I would agree with you. (07)
Comments below. (08)
Chris (09)
>-----Original Message-----
>From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx [mailto:ontolog-forum-
>bounces@xxxxxxxxxxxxxxxx] On Behalf Of Pat Hayes
>Sent: 12 September 2008 22:52
>To: [ontolog-forum]
>Subject: Re: [ontolog-forum] Thing and Class
>
>
>On Sep 12, 2008, at 1:01 PM, Chris Partridge wrote:
>
>>> Indeed. And of course, change occurs in the real world and is
>>> described by both 3-d and 4-d ontologies, but in different ways. This
>>> is so obvious that nobody felt any need to say it.
>>
>> Some of this discussion of change and 3d and 4d seems to be covering
>> (very)
>> old ground.
>
>Well, thats certainly true. The philosophy goes back to the late
>Bronze age, probably, but even as part of ontology engineering we were
>having these discussions over a decade ago.
>
>> It is my impression that in the philosophical tradition that in time
>> gave
>> rise to the short names 3d and 4d (I think these are only decades
>> old), it
>> is usual to say that the 4d view denies the existence of change.
>
>Maybe, but its still extremely misleading. I've been a 4-d guy since
>at least 1973, and I've never thought of it as denying change. In
>fact, I felt forced into it in order to be able to describe such
>changes as water pouring out of a jug onto a tabletop, or Lac Leman
>changing color from brown to blue in one weekend.
>
>> See. For example, http://plato.stanford.edu/entries/change/
>> Where it has the nice comment:
>>
>> It is on the face of it extremely implausible to deny change, but
>> extreme
>> implausibility has not always deterred philosophers. The Eleatics
>> (C5th
>> BCE), particularly Parmenides, appear to have been the first to do so.
>>
>> More recently - McTaggart, J.E., 1908, "The Unreality of Time," - with
>> Series A and B. And then a plethora of authors in the last few
>> decades.
>
>Last few decades? Citations? (010)
Are there not enough citations in the two references I gave? (Look at the
end of the papers - especially the one on temporal parts.) What more do you
want? Are you claiming that there has not been a substantial increase in
interest in the topic "in the last few decades"? If so, see later comment. (011)
The most comprehensive account of
>fourdimensionalism is probably the book by Theodore Sider, cited by
>Matthew in an earlier message in this thread: and it certainly does
>not deny the existence of change. (012)
I think you will find the book does, or at least it sits itself squarely in
the tradition that does. If you go to
http://tedsider.org/papers/ppr_4d_symposium.pdf you will find what Sider
calls a 'Precis of Four-Dimensionalism, and Replies to Critics'.
Here he says: (013)
The spatiotemporal ontology of Russell, Smart, Quine and Lewis is a blend
of separable components concerning time, persistence, mereology, and even
semantics, united by the theme that space and time are analogous:
Eternalism: past and future objects are just as real as current objects.
The reducibility of tense: tensed utterances have tenseless truth
conditions; 'now' is an indexical. (Eternalism + The reducibility
of tense is often called the "B-theory" of time.)
Four-dimensionalism: temporal parts exist. (Warning: 'four-dimensionalism'
is sometimes used instead for the B-theory, or for the Btheory+
the existence of temporal parts.)
Unrestricted composition: all objects, however scattered, have
a mereological sum, or fusion.
The worm view: continuants, i.e., the objects we normally refer
to and quantifer over, are space-time worms, that is, aggregates
of temporal as well as spatial parts
My book defends each component except the last (see the discussion of the
stage view below). (014)
As I read this, Sider is defending McTaggart's "B-theory of time" which is
also known as the unreality of time - the title of his (McTaggart's) paper.
If your point is that Sider does not explicitly mention here the 'change'
word, then look at the recent introductory books on Metaphysics such as Lowe
and Loux, where this link is clearly made. (015)
>
>BTW, there is a really good review/summary of that book here, which
>everyone should read before commenting further:
>
>http://ndpr.nd.edu/review.cfm?id=1135 (016)
Which notes these topics have been "center stage for the last few decades": (017)
A number of philosophical questions about ontology, mereology, vagueness,
identity, persistence, modality, space, and time (and also about the
relation of these issues to modern science) have been center stage for the
last few decades in the literature in contemporary analytic metaphysics. In
Four-Dimensionalism, Ted Sider presents an accessible but rigorous, highly
original, and admirably fair discussion of several of these questions as
they relate to the popular debate concerning the thesis associated with the
title of the book - informally, the thesis that objects have temporal parts. (018)
I'd also recommend Sider's home page. (019)
>
>>
>> As this and other entries in the site explain, the issue is how we
>> explain
>> the changes we see - and 3d and 4d are alternatives.
>>
>> see also http://plato.stanford.edu/entries/temporal-parts/ - Change]
>>
>> Take the definition of an ontology as the set of things that exist,
>> and we
>> start compiling our list ....
>>
>> Then in the traditional Aristotle 3d view, there are objects that are
>> changes. For example, my movement from A to B.
>
>That is a 4-d entity, not a 3-d one. There is no room for things
>called movements in a 3-d ontology. There are places where movements
>happen, and there can be movement-functions or movement-actions
>considered as state-functions, but not genuine physical space-time-
>occupying movement-things. (020)
In a so-called 3-d ontology, there are continuants and occurents (such as
Jonathon Lowe's or DOLCE (which was influenced by it). These occurents are
what do the work of 'change' - or more accurately for this view of Pat,
ontology they are changes. (021)
Perhaps a more illuminating point to consider is whether a continuant can be
moving at a point in time (irrespective to what it wad doing before or
after. For a 3d-ist this could make sense.
Similarly consider whether a continuant could change colour at a point in
time. Again, for a 3d-ist this could make sense. (022)
>
>> In the 4d view, my movement from A to B consists in my being 'at' A
>> at time
>> t1 and 'at' B at time t2 (Russell characterised this as an at-at
>> description).
>
>Wrong! That is a 3-d state-based or proposition-based view (Im not
>sure which from your description). The ability to treat a movement as
>a genuine first-class thing, as opposed to a pair of static states, is
>exactly one of the advantages of a 4-d as opposed to a 3-d ontology.
>
>>
>>
>> One can of course, and philosophers like to do it, take elements of
>> the 3d
>> and 4d view and concoct gerrymandered positions, where something
>> that looks
>> 3d has 4d elements.
>>
>> One may also take issue with the basic claim about change. But from a
>> historical point of view, I think there is a good (overwhelming?)
>> case for
>> saying that the 4d position has been characterised for some time as
>> denying
>> the existence of change (in the sense described above).
>>
>> One can add the gloss that 4d-ists (Parmenideans) did not really
>> mean that
>> change could not be described in a 4d view - but it seems to me odd
>> to claim
>> that 4d has not been characterised as denying the existence of
>> change, and
>> also to miss an insight into how the position arose, if not into
>> what it is.
>
>Maybe we are talking about different things. I have no idea how
>Parmenides got into the act, but by 4-d I mean to refer to 'four-
>dimensionalism' in the sense often called 'eternalism', which is
>simply the view that things exist extended in time: put another way,
>that physical things have temporal parts. (023)
Note Sider's point that there are, in his view, two senses of 4d and that
you need reducibility of tense as well as eternalism to get 4d.
"Eternalism + The reducibility of tense is often called the "B-theory" of
time. ... Warning: 'four-dimensionalism' is sometimes used instead for the
B-theory, or for the Btheory+the existence of temporal parts.) (024)
It is opposed to the view
>(embedded into several current high-level ontologies such as BOF and
>DOLCE), which allows for 'continuants', which are wholly 3-d but
>'continue' through time without actually occupying it. I'm pretty sure
>that is what Matthew is talking about, also. (025)
See my comments about occurents earlier. (026)
>
>Pat
>
>PS.:
>
>> BTW Pat's comment copied in at the top "of course, change occurs in
>> the real
>> world" would seem to give precedence to the 3d view that changes
>> should be
>> on our ontology list. But I have taken it out of context.
>
>OF COURSE changes should be on our ontology list. The 4-d world
>consists of very little else. (027)
Hence why some 'critics' of this approach call these process ontologies -
arguing that they only deal with processes and exclude substances. A mirror
claim to that of the unreality of changes. (028)
>
>
>>
>>
>> Chris
>>
>>> -----Original Message-----
>>> From: ontolog-forum-bounces@xxxxxxxxxxxxxxxx [mailto:ontolog-forum-
>>> bounces@xxxxxxxxxxxxxxxx] On Behalf Of Pat Hayes
>>> Sent: 12 September 2008 18:16
>>> To: [ontolog-forum]
>>> Subject: Re: [ontolog-forum] Thing and Class
>>>
>>>
>>> On Sep 12, 2008, at 1:11 AM, John F. Sowa wrote:
>>>
>>>> Dear Matthew and Pat,
>>>>
>>>> MW> The real difference is that 3D sees that what exists now is all
>>>>> that exists, whilst 4D sees the past and the future as part of
>>>>> what exists as well as the present. This is what it means to stand
>>>>> outside time.
>>>>
>>>> I agree with that description, but you seemed to suggest that the
>>>> notion of change does not exist in a 4-d view, but I think that
>>>> we were using different definitions of 'change'.
>>>
>>> Indeed. And of course, change occurs in the real world and is
>>> described by both 3-d and 4-d ontologies, but in different ways. This
>>> is so obvious that nobody felt any need to say it.
>>>
>>>>
>>>>
>>>> MW>> all spatio-temporal extents exist (at all times, but
>>>>>> strictly independent of time).
>>>>
>>>> PH> Agreed, and a nice analysis. Putting the same point in logical
>>>>> terms, the universe of discourse shouldn't be in a state of flux,
>>>>
>>>> I have no quarrel with that, but it has nothing to do with the
>>>> definition of the concept of change.
>>>
>>> BUt that, unlike the 'concept of change' , is what the thread was
>>> about until you introduced this irrelevant aside. I think you can
>>> take
>>> it that most of us don't need elementary calculus explained to us
>>> again, John.
>>>
>>>> According to the most common
>>>> definition, if time slices at t=0 and t=1 are identical, there is
>>>> no change.
>>>>
>>>> Another way to say it: if the partial derivative with respect
>>>> to the time coordinate is 0, there is no change; otherwise, there
>>>> is change in that region of space-time. The existence of change
>>>> does not imply that the global 4-d universe is in flux. It just
>>>> means that there is some region in the universe where the derivative
>>>> with respect to time is not zero.
>>>
>>> Quite.
>>>
>>>>
>>>>
>>>> MW>> And interestingly, I again use possible worlds as an
>>>> alternative
>>>>>> to modal logic. Not that I object to others using modal logic, but
>>>>>> I do not see that I am obliged inevitably to do so.
>>>>
>>>> PH> Again, I agree that this is the best approach. I think this is
>>>>> widely accepted, by the way: John McCarthy made the same point many
>>>>> years ago :
>>>>> http://www-formal.stanford.edu/jmc/modality/modality.html
>>>>
>>>> I believe that what John McC, Matthew, and Pat are recommending is
>>>> very close to Dunn's semantics for modal logic.
>>>
>>> Not McCarthy or me, I am quite sure; and given his stance on 4-d
>>> extensionality, I doubt if Matthew is either.
>>>
>>>>
>>>>
>>>> Most AI work with "possible worlds" is actually based on metalevel
>>>> reasoning about sets of propositions that describe those worlds,
>>>> not with the worlds themselves.
>>>
>>> Wrong. It is based on - it actually uses - inferences made in a
>>> theory
>>> which refers directly to the worlds. Any planner which has an
>>> explicit
>>> notion of time-interval or time-point or 'situation' (as in sit.
>>> calc., not situation theory) or world-state or context, is reasoning
>>> in a theory whose semantics is more Kripkean than Dunnian. (For an
>>> early exposition of the relationship of situation calculus to Krikpe,
>>> see section 4 of McCarthy & Hayes 1969.) None of this is based on
>>> METAlevel reasoning about sets of propositions. Of course, like all
>>> reasoning, it is PERFORMED by sets of sentences, but it is not ABOUT
>>> them.
>>>
>>>> Starting with any Kripke model
>>>> K=(W,R,Phi), where W is the set of words, R is the accessibility
>>>> relation among worlds, and Phi is the evaluation function, those
>>>> sets can be derived:
>>>>
>>>> 1. For each word w in W, define the facts of w as the set of all
>>>> propositions p that are true in w: {p | Phi(w,p) = True}.
>>>>
>>>> 2. Define the laws of w as the set of all propositions p that are
>>>> necessarily true; i.e., p is true in all worlds accessible from
>>>> w.
>>>>
>>>> 3. Define the accessibility relation R(w, w') as True iff every
>>>> proposition p that is necessarily true in w is also true in w'.
>>>>
>>>> This construction replaces every world in a Kripke model with a set
>>>> of laws and facts in a Dunn-style model. Any theorem that can be
>>>> proved about a Kripke model is also true of the corresponding Dunn
>>>> model. But Dunn's version is more *usable* because it makes the
>>>> laws and facts available for further analysis and manipulation.
>>>
>>> Nonsense. Not only is Dunn's version not more usable, it is not in
>>> fact used. The laws and facts are stated explicitly as sentences in
>>> theories using Kripke-style semantics. Check out any of the hundreds
>>> of papers on planning using a situation-calculus style of
>>> representation.
>>>
>>>> PH> John's way follows Dunn's theory and is based on intensional
>>>>> descriptions. The far more commonly used view uses Kripke's
>>>>> possible-worlds account of modalities. Kripke's is widely accepted
>>>>> as the standard, and certainly gives a more usable semantics...
>>>>
>>>> Not true. Nobody actually implements "possible worlds"
>>>
>>> I never said they did. They implement systems which reason, using
>>> formalisms which refer to possible worlds. Remember, we are talking
>>> here about SEMANTICS, not implementation.
>>>
>>>> . What they
>>>> implement and reason with and about are sets of statements of the
>>>> laws and facts of those worlds.
>>>
>>> Yes, exactly. And the question is, what is the appropriate SEMANTICS
>>> for those statements? Answer: they REFER TO possible worlds. They do
>>> not refer to sets of sentences; they are not in a METAtheory.
>>>
>>>> Since the above construction can
>>>> map any Kripke model into such sets, most people who implement such
>>>> systems pay lip service to Kripke's version, but they actually use
>>>> something that is much closer to Dunn's version.
>>>
>>> They - and here I speak as one of them - use Kripke-style semantics
>>> when doing semantic analysis. They do not, as a broad rule, use Dunn-
>>> style semantics. In fact, I do not know of any significant body of
>>> work in AI planning based on Dunn-style semantics. I believe you are
>>> the only writer who argues for Dunn's model in this context.
>>>
>>> Pat
>>>
>>>>
>>>>
>>>> For further discussion of these and related issues, see
>>>>
>>>> http://www.jfsowa.com/pubs/laws.htm
>>>> Laws, Facts, and Contexts
>>>>
>>>> http://www.jfsowa.com/pubs/worlds.pdf
>>>> Worlds, Models, and Descriptions
>>>>
>>>> John
>>>>
>>>>
>>>> _________________________________________________________________
>>>> Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
>>>> Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-
>forum/
>>>> Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
>>>> Shared Files: http://ontolog.cim3.net/file/
>>>> Community Wiki: http://ontolog.cim3.net/wiki/
>>>> To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx
>>>>
>>>>
>>>>
>>>
>>> ------------------------------------------------------------
>>> IHMC (850)434 8903 or (650)494
>>> 3973
>>> 40 South Alcaniz St. (850)202 4416 office
>>> Pensacola (850)202 4440 fax
>>> FL 32502 (850)291 0667 mobile
>>> phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
>>>
>>>
>>>
>>>
>>>
>>>
>>> _________________________________________________________________
>>> Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
>>> Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-
>forum/
>>> Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
>>> Shared Files: http://ontolog.cim3.net/file/
>>> Community Wiki: http://ontolog.cim3.net/wiki/
>>> To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx
>>>
>>
>>
>> _________________________________________________________________
>> Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
>> Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
>> Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
>> Shared Files: http://ontolog.cim3.net/file/
>> Community Wiki: http://ontolog.cim3.net/wiki/
>> To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx
>>
>>
>>
>
>------------------------------------------------------------
>IHMC (850)434 8903 or (650)494 3973
>40 South Alcaniz St. (850)202 4416 office
>Pensacola (850)202 4440 fax
>FL 32502 (850)291 0667 mobile
>phayesAT-SIGNihmc.us http://www.ihmc.us/users/phayes
>
>
>
>
>
>
>_________________________________________________________________
>Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
>Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
>Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
>Shared Files: http://ontolog.cim3.net/file/
>Community Wiki: http://ontolog.cim3.net/wiki/
>To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx
> (029)
_________________________________________________________________
Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
Subscribe/Config: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/
Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/
To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx (030)
|