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Re: [ontolog-forum] Two ontologies that are inconsistent but both needed

To: "Cassidy, Patrick J." <pcassidy@xxxxxxxxx>
Cc: ontolog-forum@xxxxxxxxxxxxxxxx
From: Pat Hayes <phayes@xxxxxxx>
Date: Mon, 11 Jun 2007 15:21:10 -0500
Message-id: <p0623090dc29351d92003@[]>
>Pat H -
>    Could you explain the logical factors that prevent one from equating
>a zero-length time slice of a 4-D object to a 3-D object?    (01)

You can equate it with a 3-d object: in fact, it 
is a 3-d object (at a particular moment). But you 
cannot equate it to a continuant.    (02)

>  It appears
>that that is what you were saying:
>>  Just as 3-d entities have 2-d surface and sections, these things have
>>  3-d 'surfaces' and 'sections'. A 3-d section of one of them is an
>>  instantaneous snapshot of it, a freezing of it at a moment in time.
>>  (If that moment is understood to be 'the present', then at that
>>  present time, this section is very similar to a continuant, although
>>  it cannot actually be the continuant for essentially logical
>>  reasons.)
>  . . . But I haven't seen the arguments for that.    (03)

In a nutshell.    (04)

A continuant is (according to various authorities):
1. 3-d, purely spatial, having no temporal extent, parts or aspects.
2. Exists at various times, and has no temporal location, because...
3  ... it endures through time while retaining 
its identity. That is, its the *same* continuant 
at one time as at another.    (05)

A timeslice (3-d section of a 4-d spatiotemporal thing) is:
1. 3-d, with a spatial extent, but also with an associated time.
2. Exists at one time only, and is temporally located at that time.
3. Does not endure through time, and is not identical to any other timeslice.    (06)

So for example, consider me (Pat) now. Lets say 
that I am a continuant. Wait a minute. Now 
consider Pat again. I'm still the same 
continuant. There is just one of me.    (07)

Now do the same experiment talking about 
timeslices. The first slice is Pat-at-t, say, and 
the second slice is Pat-at-(t+1). These are not 
identical (they are at different times). Neither 
of them is identical to the continuant, because 
if one of them were then the other would also be, 
so they would be identical.    (08)

That is the logical reason I was referring to. 
One could think of a timeslice as a 
continuant-at-a-time, were it not for the fact 
that this mode of expression is ruled out by the 
standard dogma, which insists that continuants 
cannot have temporal 'parts', since such a slice 
would be a temporal part of me. At this point one 
is typically directed to think of a slice of my 
life, the 'occurrent' version of me. Which is 
fine: my point is that this is what I have been 
all along. Anything I want to say about Pat can 
be said about the occurrent version of Pat, the 
Pat-life. This is the thing that has 3-d slices. 
I don't need the continuant Pat. I can have, 
purely for intuitive convenience, a 'thing' that 
is Pat and which is the same thing at different 
times, so writing things like    (09)

(age Pat t)    (010)

to mean the age of Pat at time t; and we can call 
this Pat a continuant if you like; but it is not 
a strict Simons/Smith continuant, since it can 
also be viewed as having temporal parts, so that 
I can also write    (011)

(age (slice Pat t))    (012)

i.e. speak about the t-episode of Pat.    (013)

A continuant is something like a 'moving slice' 
of the 4-d Pat, which is the same slice as time 
goes on, retaining its identity as it moves [1]. 
This idea makes sense in the A-series view of 
time where one understands assertions to be made 
in a 'moving present', distinguished from 
assertions about the past and the future, a world 
where tenses make sense. Natural language is 
often organized this way, perhaps because it 
evolved mostly to convey information about the 
actual present circumstances. But it is a very 
poor way to try to state an ontology, for 
whatever one says or writes is immediately made 
wrong since after a very short time it is about 
the past rather than the present. If you want 
your words to be archived, it is better to use 
the B-series view (see 
http://en.wikipedia.org/wiki/B-Theory_of_time for 
this terminology) of a time-line, in which time 
is treated as a dimension and events and things 
are placed on it or in it by a date/time 
convention. Continuants are a vestige of the 
A-series way of talking which do not properly fit 
into a B-series metaphysics. The point being that 
there are no 'moving slices' in the 4-d world: 
the notion does not make sense.    (014)

My complaint can be summarized thus. When writing 
ontologies we cannot manage without the B-series 
view. We cannot write ontologies in a 'present 
tense'. So our options are to use the B-series 
view, or to try to use both. I suggest that it is 
better to make a clean choice of the B-series as 
the single temporal framework than to try to mix 
the two notions together, as they (notoriously) 
do not mix. This may indeed have the consequence 
that certain very familiar modes of expression in 
natural language do not map directly into the 
ontology. But the engineering advantages of a 
clean, coherent, internally consistent temporal 
framework outweigh the resulting artificiality; 
particularly as one can get used to it quite 
quickly. Much of the basic thinking here was done 
by McTaggert in 1927, by the way, and it seems a 
shame to throw away all that good insight.    (015)

Pat H.    (016)

[1] Years ago when this issue came up in the SUO 
discussions, I tried to see how to map between 
the two modes of expression by finding a common 
description which both could agree on the formal 
theory of, but would interpret with a different 
metaphysics. I came up with the idea of a 'entity 
movie'. This is a temporally ordered *set* of 3-d 
things, which can be viewed by one player as 
simply being Pat, and by the other player as 
being the Pat-slices. The 4-d view is then got by 
thinking of this movie as the set of slices of a 
4-d entity, and the continuant view is got by 
describing it as a series of views of a single 
continuant. I tried this idea out on several 
people, of various views, and they all agreed 
that it made a kind of sense from their 
perspective. So I set out to formalize the 
notion: and what I found is that this 'movie' 
might as well actually be the occurrent as far as 
the formalism is concerned. A 'frame' of the 
movie is defined by a name used to refer to one 
thing at different times, and a time-reference: 
(Pat + t). What is this '+', in the formalism? 
Well, you could write it like this    (017)

(slice Pat t)    (018)

where slice is a function (from things to their 
slices), or you could say that the 't' is an 
index used to make assertions about Pat, as for 
example    (019)

(= (age Pat t) t)    (020)

where 'age' is a fluent with a temporal 
parameter. So what it boils down to is a choice 
of where to put the temporal parameter: inside 
relations or inside functions. If I am a 
continuant I don't have slices, so 't' *must* go 
into the relational argument position. Or I can 
be allowed to have slices, and then it can be put 
anywhere.    (021)

All that argument and debate and citing of 
authority, and it all boils down to this?? Yes. 
This is all it amounts to in the actual ontology: 
allowing slices or not. Not a matter worth 
spending any more time on, seems to me. Sure, 
allow them. Or don't. I don't really care: 
nothing depends on it; NOTHING. One can 
trivially, mechanically, translate from the 
continuant-anal formalism into the more relaxed 
one, without losing a gram of expressivity and 
making the axioms simpler.    (022)

See why I get impatient with metaphysics and philosophy?    (023)

:-)    (024)

>Patrick Cassidy
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