>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:
>
>[PH]
>> 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)
>
>PatC
>
>Patrick Cassidy
>CNTR-MITRE
>260 Industrial Way West
>Eatontown NJ 07724
>Eatontown: 732-578-6340
>Cell: 908-565-4053
>pcassidy@xxxxxxxxx
>
>
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