Sometimes you stumble across a paper that needs to
be replied to, but you think that you’re not the right person to write it. This
happens to your humble correspondent not a lot, but it happened this morning.
The paper in question is so potentially misleading and confusing that I
hesitate even to link to it.

   — But I linked to the overpaidblog
yesterday, surely this isn’t worse.
   — That was as the punchline to a
joke, a very funny one if you ask me.
   — Well how is anyone going to respond
to the paper if there’s no link?
   — Hmmm … I hate it when my electronic
conscience is right. Well, here’s the link.

The gist of the paper is…

I mean, the main argument is…

It’s too hard to paraphrase without my head
exploding. The conclusion of the paper is that 3D and 4D theories are
terminological variants. Or I should say, the conclusion of the paper is “the
3D and the 4D descriptions of the world are equivalent, in a clear and precise sense
to be explained, and that it is not a question of one being true and the other
false,” because it’s not clear that disquotation preserves meaning here. The
problem is that it’s very hard to tell from the paper whether the 3D and 4D
theories are meant to be theories about endurance or theories about the reality
of the past and future.

For those who haven’t been following this debate
(which is probably no one on this blog) some quick distinctions.

Eternalism is the thesis
that the past, present and future are real.

Presentism is the thesis
that only the present is real.

Endurantism is the thesis
that (some) things persist through time by being wholly present at many times.

Perdurantism is the thesis
that things that persist through time do so by having parts at each of the
moments of time at which they exist.

Now the terminological fun starts. In America,
normally, ‘three-dimensionalism’ means endurantism, and ‘four-dimensionalism’
means perdurantism. Outside America, things are not so clear. So in Australia,
one can write papers with titles like “Must a Four-Dimensionalist
Believe in Temporal Parts?”, without the answer being, trivially, yes,
because ‘four-dimensionalism’ can mean eternalism,
rather than perdurantism, there. (Not that it always does mean
that, but it can.) And, of
course, there’s no immediate clash between eternalism and endurantism – indeed
a lot of very smart people believe in both.

So when this paper says that it believes there’s an
equivalence between 3D and 4D theories, does it mean an equivalence between
eternalism and presentism, or between endurantism and perdurantism? Well, the
paper starts like it’s the former. They line up lots of famous people on either
of the ‘3D/4D’ debate and they seem to more or less entirely split on whether
they are endurantists or perdurantists. So far so clear. But then things get
hazy. They quote Craig discussing Einstein as follows:

‘the seriousness with
which Einstein took [the four-dimensional] conception may be seen in the fact
that when his life-long friend Michael Besso died, Einstein sought to comfort
his bereaved family by reminding them that for physicists Besso had not ceased
to exist but exists tenselessly as a permanent feature of the space-time
reality’

The material in square brackets is their insertion,
not mine. Now whether Besso ‘exists tenselessly as a permanent feature of the
space-time reality’ turns on whether eternalism or presentism is true, not on
whether endurantism or perdurantism is true. So maybe by four-dimensionalism
they mean eternalism. So I don’t know what’s going on here.

Ted Sider has argued at some length that these
equivalence theses must be wrong because three dimensionalists (i.e.
endurantists, we’re back in American writing now) and four dimensionalists
disagree about how many things there are. And since we can state disputes about
how many things there are in a neutral language, the language of first-order logic
with identity, this is a substantive and not a semantic dispute.

          —
But semantic disputes are real disputes.
          — Not in metaphysics papers they
aren’t, dear conscience.

So, for example, we can say that there is more than
one thing in the world by just saying $x $y (x ≠ y). When
people say there’s no substantive disagreement between two people who disagree
about whether there is more than one thing in the world, the right response is
to shake them by the collar and say, “What part of $x $y (x ≠ y) don’t
you understand, ya punk?” Arguably, people who say there is no dispute between
three and four dimensionalists are making the same mistake writ large.

To be
fair to the paper, there is an interesting discussion of the twins paradox at
the end. I don’t know how this is meant to connect to the 3D/4D dispute, but
then since I don’t know what that dispute was, that’s none too surprising. But at
a glance I’d say there’s some independently valuable material, and links to
other valuable material, in those pages.