[Top] [All Lists]

Re: [ontolog-forum] Context, at last!

To: ontolog-forum@xxxxxxxxxxxxxxxx
From: Chris Menzel <cmenzel@xxxxxxxx>
Date: Wed, 15 Jun 2005 16:37:48 -0500
Message-id: <20050615213748.GK22478@xxxxxxxx>
On Mon, Jun 13, 2005 at 10:18:01AM -0700, Nicolas F Rouquette wrote:
> -----------------
> 'de dicto' and 'de re': Following [Hayes04], the contrast between de
> dicto (of the speech) and de re (of the thing) can be illustrated by
> the distinction between direct quotation of speech, as in "Louis said,
> 'Superman is Clark Kent' " vs.  "Louis said that Superman is Clark
> Kent" . The first, de dicto, reports Louis' actual words (and is
> false, in the story) while the second, de re, reports what she said
> about someone, using the speaker's words ....    (01)

This example is a better illustration of the distinction between direct
and indirect discourse -- reporting what speaker literally said vs
reporting the *content* of what is said.  That is, of course, a very
interesting distinction, but it's not coextensive with the de re / de
dicto distinction.  The dr/dd distinction usually arises in modal or
other so-called "intensional" contexts, and typically involve the
interplay of modal or intentional concepts and quantification.  For
example, if I tell you "I'm worried that someone is watching me", what
I've said is ambiguous depending on whether there is some specific
individual that worries me (de re), or whether my concern is simply that
someone or other -- I don't know who -- has me under surveillance (de
dicto).    (02)

The logical interplay noted above in this case has to do with the scope
of the existential quantifier vis-a-vis the intentional verb "worried".
The quantifier has "wide" scope on the de re reading, and "narrow" scope
on the de dicto; in a KIF-ish syntax:    (03)

De re: (exists (?x) (IsWorried Menzel [IsWatching ?x Menzel]))    (04)

De dicto: (IsWorried Menzel [exists (?x) (IsWatching ?x Menzel]))    (05)

One of the interesting things about intentional (hence de re and de
dicto) contexts that can be seen here is that their proper
representation often seems to require reifying *propositions* -- the
things worried about, believed, feared, desired, etc.  For this reason
worry, belief, etc are often called "propositional attitudes".  I've
used square brackets above as a mechanism for forming a
proposition-denoting term out of a sentence.  (There are other ways to
do represent intentional contexts, but this one is clear and pretty well
studied.)    (06)

The dr/dd distinction is also prominent in modal logic.  Typically (and
very informally), a de dicto proposition involves the attribution of a
modal property (notably, necessity or possibility) to a general
proposition, whereas a de re modality involves the attribution of a
modal property to a specific individual.  Here's a simple example from
medieval philosophy concerning an argument that God's foreknowledge of
the future is incompatible with human free will.  Consider any simple
action that ostensibly seems free, say, whether or not one sits at a
given moment.  God, of course, being omniscient, knows today who is and
who is not sitting tomorrow at noon.  Consider, then, the following
argument:    (07)

1. Whoever God sees to be sitting at noon tomorrow is necessarily
   sitting at noon tomorrow.
2. God sees that Bill Clinton will be sitting at noon tomorrow.
3. Therefore, Clinton is necessarily sitting tomorrow.
4. If Clinton is necessarily sitting tomorrow at noon, he is not free 
   to refrain from sitting tomorrow at noon.
5. Therefore, Clinton is not free to refrain from sitting tomorrow at
   noon.    (08)

Of course, the sort of argument can be framed for any individual and any
action.  So it looks like God's foreknowledge is incompatible with human
freedom.    (09)

St Thomas responded to this argument by showing that it hinges upon a de
re / de dicto ambiguity.  Specifically, Premise 1 is ambiguous between:    (010)

1a. (Nec (forall (?person)
                 (=> (Sees God [SittingAtTime ?person TomorrowNoon])
                     (SittingAtTime ?person TomorrowNoon))))    (011)

1b. (forall (?person ?time)
             (=> (Sees God [SittingAtTime ?person TomorrowNoon])
                 (Nec (SittingAtTime ?person TomorrowNoon))))    (012)

(Note we have a similar sort of scope ambiguity here as in the first
example, this time between the modal operator "Nec" and the universal
quantifier.)  1a is just an instance of the logically trivial (given
that God is omniscient, of course) de dicto proposition that,
necessarily, whatever God sees will be the case will, in fact, be the
case.  1b, by contrast, is the dubious de re proposition that if God
sees that someone will be sitting tomorrow, then that person is
*necessarily sitting tomorrow*; i.e., that person is sitting tomorrow in
*every possible world*.  Unlike 1a, 1b is implausible; but 1b is the
reading of premise 1 that is needed for the argument to go through.
Thomas therefore concluded that free will was still safely in tact.    (013)

Of course, there are lots of examples not involving medieval
philosophical theology, but they are rather bland and joyless by
comparison. :-D    (014)

Chris Menzel    (015)

Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/ 
To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx    (016)

<Prev in Thread] Current Thread [Next in Thread>