Subjunctives-- and whatever else possible worlds are meant to do -- can be
done perfectly well without possible worlds, as witness the fact that they
are handled in all natural languages without once resorting to possible
worlds.
(The nearest thing to a successful use of possible worlds in an object
langauge is the sentence labeling within "proof" in modal Dialogic, where
the
whole is merely a convenient device and exists only in proofs, never in
sentences outside the proof context; sentences have only possibility and
necessity operators. Happily there now are ways to get around even this use
in almost every case.)
Without possible worlds, what resources are left -- what do natural
languages
use? For the most part (and without making an actual survey -- other
patterns would be welcomed), four patterns seem to predominate: tense,
condition, causation, and imagination (well, some mental activity).
Naturally, I prefer tense, but it is so SAE that I did not want to throw it
to the groups that thinks that anything SAE is ipso facto not Lojbanic.
Lojban has at least considered the other three: {va'o}, {bai} and {da'i}
(and
has put {mu'ei} in a tense-related selma'o}.
Lojban is, of course, totally inspecific about the nature of time, but, if
we
wanted to do a metalinguistic explication of tense structure, we would
almost
certainly use one with linear past and branching futures. At least, the
future would branch at kairoi,crucial events. The tense subjunctives tend
to
go back to such a kairos and then leave it along another temporal path,
defined by a different outcome at the crisis, and come the same distance
forward on that path as back on the other. From the viewpoint of this
alternate now, the different world can be viewed. (The forms used for this
are usually obsolete ones, so subjunctives are good digging ground for the
history of tense systems.) This system then gets expanded to the general
case (as do all of these) of any contrary-to-fact or hypothetical
situation,
even if it is not temporally connected to the present or a past kairos.
So,
{puba} would not make a goodcandidate for subjunctives in general, though
something related to it might have the advantage of cutting off a
particularly useless kind of speculation, the "If Socrates were a 17th
century Irish washerwoman" sort, where all connections with anything
recognizable are severed, making defensible continuations impossible
(without
a lot of assumptions not mentioned in the condition). Technically, a tense
system subjunctive system needs two tenses: an establishing one for the
kairos' other outcome, and one for the alternate now; the rest are normal
tenses around these two. And, of course, the alternate now need not appear
when it is clearly linked in with the kairos form nor in the subsequent
sentences. But a comback form is needed to get out of the subjunctive
situation (presumably the one for complex tense situations would do).
Tense
are obviously most natural for contemplating what might have happened if,
HIBK and the like. They work literally only if we allow going back even to
the Big Bang (the ultimate kairos) and coming out along alternate settings
of
the physical constants, say.
The causal version has its natural home in general laws and their
applications but is then expanded to cover cases where causality plays less
to no role -- that can be used anyhow. "If I dropped this pencil it would
accelerate pretty damned close to g" is natural for it; "If Socrates had
escaped from prison, he would never have been famous" works with the loose
notion of causality or law that holds in the social sciences; "If Scrates
were a 17th century Irish washerwoman,..." is straining the idiom a bit,
because no laws are apparently to be applicable (either Socrates or the
woman's situation seem irrelevant). As with the tense case, we would need
a
sign that brings us back from the hypothetical realm to the real -- or,
perhaps more naturally, a device that indicates that the hypothesis is
still
in play, since causal forms are typically one-sentence idioms (sumti of a
causal predicate or BAI and a clause) or connectives that only connect two
sentences, not easily more except in a cusal sequence: this and so this and
so this. And, of course, the claim that this would happen if that had is a
separate one from a strictly causal claim (in many cases); it may be true
even if the causal claim is false. The choice of {bai} for this seems to
me
particularly unwise, since, while it is a very general causal notion, it is
also a very strong one, inappropriate from many subjunctive uses, where
only
plausibility or, at best, probability are at play.
The mental model has somewhat the opposite, supposing knows no limits from
the real world -- we can suppose they did not apply. To be sure, except
when
one is composing fantasy for entertainment, there is usually a practical,
this-world, point and so we cannot dismiss all constraints. But the
at-home
use of imaginational subjunctives is more open to the tests of plausibility
and the like than to laws. And it lends itself more naturally to developing
hypotheticals, adding new conditions on as the discussion moves along. It
is
ideal for brainstorming, then, but can, of course, be adapted to other
patterns. While I like the framing {da'i} - {da'inai} for contained uses
like indirect proof, they are a useful pattern for subjunctives of the
imaginary sort as well.
Every subjunctive starts by setting up a condition, around which the rest
of
the subjunctive discussion revolves. Thus, a device that introduces the
condition is a natural beginning of any subjunctive. But that condition
does
not have to be temporal or causal or even imaginary (though not holding at
the moment), so a general "what happens if this condition obtains?" seems
the
most complete basic subjunctive form, assuming there are ways to continue
it
and get away from the hypothesis generally. This is why I favored {va'o}
for
this purpose. I wasn't stuck on it, but it seemed to move in the right
direction more literally than the other choices. On the other hand, I now
appreciate the factual uses of {va'o} and would not like to lose them just
to
get a subjunctive. So, I think that, if we want a general subjunctive,
something like {va'o} is the way to go.
On the other hand, I am not sure we want a general subjunctive. As I have
mentioned in the above paragraphs, there seem to be a number of uses for
the
subjunctive, similar in some ways, differing in others. And especially
differing in what is going to constitute a true subjunctive claim,
something
that a logical language ought to take quite seriously. That thought seems
to
lead to sugtgestion that we open up a variety of subjunctives -- at least
historical, causal and speculative -- and deal with them separately. It
may
turn out that not all of them need subjunctives at all (causal ones do seem
to be pretty easily converted to indicatives, some would say), but for
those
that do, we can devise a starter (the condition), a continuer, and an
ender.