It is easy to overlook that David Lewis has revised his worm view of ordinary things in 'Tensing the Copula', Mind 111 (2002). Here is the passage (p.5):
In talking about what is true at a certain time, we
can, and we very often do, restrict our domain of discourse so as to
ignore everything located elsewhere in time. Restricted the domain in
this way, your temporal part at t_1 is deemed to be the whole of
you. So there is a good sense in which you do, after all, have *bent simpliciter*.
In other words: Terms for ordinary things are indeterminate. They don't always pick out worms. Sometimes they pick out segments, and sometimes just stages, depending on the contextually determined domain of discourse.
I think this is an improvement over the worm theory. Is it general enough? Lewis says that our terms pick out the sum of all those temporal parts of the relevant worm that are inside the domain of discourse. But don't we also attribute bent-simpliciter to the whole of me in "I'm bent now, but I wasn't bent yesterday"? Yet here the domain contains yesterday's parts as well.
Brian Weatherson now says that 'the world exists' is exactly as natural as
'there is a G', where G applies to worlds that are exactly like this one.
I agree. But this only makes things worse, because the class G denotes
seems very natural: It contains our world and all its exact intrinsic
duplicates. Is this a gruesome gerrymander? We still need a
further restriction on best theories apart from naturalness.
Intuitively, some objects are more natural than others. For example, cats
are more natural than mereological fusions of cats and elephants. I think
that ultimately, naturalness of things should be definable in terms of
naturalness of the properties the things instantiate. I'm not quite sure
how exactly this is to be done, so for now I'll stick with the intuitive
notion of naturalness. Intuitively natural things are spatiotemporally
connected, constitute a causal unity, contrast with their surroundings,
etc. The world, that is, the mereological fusion of everything that exists
at any spacetime distance from us, does fairly well here: As far as I know,
it is perfectly connected, causally united (indeed, causally closed) and
contrasts clearly with everything outside of it (such as numbers or other
worlds, if such there be). Why then does Brian Weatherson think that the
world is gruesome?
I see two ways to exclude 'the world exists' as the best theory of
everything. The first is the one I already mentioned: to state that a good
theory must imply interesting truths a priori. The second is to
stipulate that a theory must not contain individual constants. I have some
sympathy with such a stipulation, though it may stipulate away haecceitism.
It is sometimes (e.g. in David Sanford, 'Fusion Confusion', Analysis 63,
2003) said that some things are not fusions of all their parts: cats
and fusions of cat-parts for instance seem to differ in tensed and modal
properties. It may be noteworthy that on the standard definition of
'fusion', this position is outright inconsistent: X is the fusion of
Y1,Y2,... iff all of Y1,Y2,... are parts of X and no part of X is
distinct from all of Y1,Y2,.... Hence if X is not the fusion of
Y1,Y2,... then either one of Y1,Y2,... is not a part of X or some part of
X does not overlap Y1,Y2,.... So nothing can possibly fail to be the
fusion of all its parts.
In her paper 'Logical
Parts', forthcoming in the december issue of Nous, L.A. Paul presents a nice
theory of objects according to which things are mereologically composed of
their properties. Here are a couple of potential problems.
First, the theory seems to conflict with Unrestricted Composition and
incompatible properties. For suppose that P and Q are incompatible
properties, like being square and being round. By Unrestricted
Composition, there is a fusion of P and Q (or, if you prefer, of P and Q
and Paul's red cup). This fusion has both P and Q as parts, hence, on
Paul's theory, it is both P and Q. But if P and Q are incompatible, nothing
can be both P and Q.
I have the vague impression that Lewis' paper 'Things qua truthmakers', and
in particular the appendix by Lewis and Rosen, proves something important.
But I'm not sure what it is. Maybe it's that the request for truthmakers
was thoroughly misguided in the first place.
The problem is that the truthmaker principle is saisfied so eaily: Let 'w'
be a name for our world that does not apply to any qualitatively different
world, nor to anything inside any world. (That is, 'w' denotes our world
under a rather strict counterpart relation.) Let T be any qualitative
truth. Necessarily, if w exists, then T, since otherwise 'w' would be
applicable to a world in which not-T, even though T holds at our world,
contrary to the rule just stated. Hence w is a truthmaker for T, that is,
for any truth whatsoever.
Let T be any theory. If you worry about T's overabundant ontology, there is
a simple way to translate it into a theory T_i with a very sparse ontology:
For every sentence S in T introduce a new primitive predicate P that
applies to a world w iff S is true at w. Then replace S by 'the world is
P'. A more elegant method would not introduce a new primitive predicate
for every sentence, but rather use structured predicates, that are
systematically built up in the way the sentence is built up. (See Quine,
'Variables explained away', and Prior, 'Egocentric Logic'). T_i is a
theory that says the same as T with an ontology of just one individual -
the world. The price to pay for this reduction in ontology is an
overabundant ideology: Who wants all these weird predicates? Nobody.
A number of people have noticed that the problem about probability I mentioned last week is not really a problem about infinite probability spaces, but rather about possible distributions over such spaces. For instance, a Gauss distribution over the reals
will yield well-defined probabilities at every interval. But in the case of
the arbitrary real number, the distribution would have to be a line parallel to the x-axis, and how could the segments of the area under this line possibly add up to 1?
I'm still not sure if talk about
probability really does not make sense in such cases or if it does, but
we (or at least I) lack an adequate mathematical treatment. For example, are the following
three conditions logically inconsistent?
1. Atom A will decay at some time in the future.
2. The probability of decay at any day is the same as at the preceeding day.
3. Future is infinite.
Just in case anyone reading this blog is also interested in Lewis exegesis, Dave Chalmers usually knows the answers to my questions: The answer to the question raised at the end of this posting, whether Lewis himself believes the deducibility
claim he attributes to Jackson, is 'yes'. And about mental properties, apparently Lewis still prefered the realizer view in 1998.
Supervaluationsism and structuralism ('eliminative structuralism', not
the kind of structuralism that postulates structures) almost coincide.
Structuralism about something t says that any sentence 'F(t)' is to be
interpreted as 'for all x (if x is a candidate for t then F(x))'. For
example, arithmetical structuralism says that '2+2=4' is to be interpreted
as 'for all [N,0,',+,.] (if [N,0,',+,.] satisfies the peano
axioms then 0''+0''=0''''). If we translate 'x is a candidate for t' as 'x
is the referent of a precisification of 't'', we get: F(t) is (super-)true
iff it is true on all precisifications of 't'.