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Adding to my last posting, mehr Licht?
Another feature of opaque contexts, which I forgot to men-
tion, is that Leibnitz's Law does not work in them: from a=b and
[a] we cannot infer [b]. This is certainly the case if one term
of the identity is a description, since what fits (or is intended
to fit) a description can vary with context. It is less certain
for proper names, since some logicians hold that names are rigid
designators, referring to the same thing in all contexts (at
least all those in which the thing named exists). But proper
names in natural languages do not seem to meet this requirement
-- more than one thing can have the same name, for example, even
in a single context. Thus, ordinary proper names seem to behave
pretty much like descriptions under this rule (as the Lojban
placement -- and official reading -- of _la_ suggests) and had
best be thought not to be replaceable under identity.
I found in the avalanche of the last couple of weeks a note
from lojbab that mentions that the mark for raised subjects is
_tu'a _, which is then the opacity marker under the suggestion in
that posting (_xe'e_ in its non-experimental form).
OTOH some expressions in English contain event-referring
expressions but seem to be transparent: " I saw someone shooting
pool," for example. This pretty clearly does imply that there is
someone that I saw shooting pool. Indeed, if it could be shown
that there was no one shooting pool in my visual range, I would
have withdraw my original claim, falling back to "I thought I
saw..." or "It looked like ..." or whatever. But notice that
the basic claim is not exactly the classic English form of an
event-referring expression, a "that"-clause or an infinitive. "I
saw that someone was shooting pool" does seem to be opaque,
approximately equivalent to "came to know ... by seeing" and so
inheriting the opacity of "know," failing to export when I could
not identify the player -- presumably by sight. Thus, we might
argue that the object of "see" in the transparent case is not the
event but rather just the subject, to which the event-reference
is somehow attached. That is, it may be that the analysis of "I
saw someone playing pool" is not "I saw (someone playing pool)"
but "I saw someone (playing pool)", which would both account for
the transparency and fit in with our general notion that the
object of seeing is an object not (generally) an event. That
leaves the question of how the "someone" and the "playing pool"
are to be linked together, for it is not just that the someone
was in fact playing pool but that I saw him doing it, so there is
an event-referring expression here after all, though perhaps
subordinately. None of the obvious suggestions in Lojban (e.g.
_poi_ or _noi_) seems quite right. Comments and suggestions
welcomed eagerly.
pc>|83