Friday, June 03, 2011

de re et de dicto.

Okay, after trying to get to the bottom of the difference, it seems to me that it amounts to this:

de re is when we’re talking about a thing.

de dicto is when we’re not talking about a thing but a proposition.

In the philosophy of language this distinction is important because it helps us disambiguate what we might mean when we ascribe beliefs to agents. Suppose we say

(1) Jim believes that “someone stole my bananas.”

The problem with (1) is that the scope of ‘someone’ is ambiguous between someone in particular vs. someone in general. It could be that Jim is thinking of somone in particular, let’s say Sam, in which case (1) should be read as

(1’) Jim believes that “Sam stole my bananas.”

In (1’), what Jim believes is that someone (a thing) named ‘Sam’ stole his bananas. Since Jim has a particular thing (Sam) in mind, (1) read as (1’) is ascribing a de re belief to Jim.

But suppose that Jim has reason to think someone stole his bananas, but he doesn’t know whom. If this were the case then (1) should be interpreted to as

(1’’) Jim believes that “some person or other stole my bananas.”

Because in (1’’) Jim doesn’t have any particular individual in mind, what he believes is that a particular proposition is true, namely that “some person or other stole my bananas”. Because Jim believes a certain proposition is true and not something of some particular thing, (1’’) is ascribing a de dicto belief to Jim.



Armed with this distinction, I’d like to flesh out more fully my attempt to dissolve the sentential liar’s paradox.

(2) Sentence (2) is false.

Supposedly, if (2) is true, then it’s false, for to say of itself truly that it is false is to say something false. But, if (2) is false, then it is true, for if (2) is false, then it says something true of itself, and is therefore true. And hence the paradox.

My objection amounts to this: the collection of symbols that includes and follows the first instance of the symbol ‘(2)’ above is a concrete thing, just like ‘my desk’ and ‘jcw’. Being a mere thing (res) it cannot be true or false anymore than ‘my desk’ and ‘jcw’ can be true or false. Why not? Well, truth and falsity are predicates not of concrete things (de rerum), but of propositions (de dicta). That is, propositions like “the house is red” and “jcw is generally cool” can be true or false. Furthermore, there cannot be propositions unless there are concrete things that do or do not have “ordinary” predicates. That is, the existence of any and all propositions with ‘jcw’ as the their subject depend on the concrete existence of ‘jcw’ and whatever “ordinary” predicates he may or may not have (e.g., jcw’s being generally cool, and the like). Once there is the state of affairs jcw’s existing a whole slew of propositions can thereby exist and be true or false, depending on whether they accurately describe the thing jcw. In sum, since the collection of symbols that includes and follows the first instance of the symbol ‘(2)’ above is a thing (res) and not a proposition (dictum), it cannot be true or false. And since it is neither true nor false, is no more paradoxical than (and equally meaningless as) saying“jcw is false”.

“Well,” I hear someone asking, “if the collection of symbols that includes and follows the first instance of the symbol ‘(2)’ above cannot be true or false, can’t the following proposition be true or false?”:

(3) Proposition (3) is false.

No, (3) can be neither true nor false because (3) is not a proposition. In order for it to be a proposition it needs to have a concrete thing (res), and not a proposition, as its subject. And furthermore, for (3) to be true or false the predicate said of the concrete thing acting as its subject must be an “ordinary” one, unlike truth and falsity. As such, there is no such proposition denoted by (3), and hence, the non-proposition (3) ispso facto cannot be true or false. And if it’s neither true nor false, it cannot be paradoxical.


Now onto modality de re and de dicto. From what I can tell the difference is whether a modal predicate (i.e. necessary, contingent, possible, impossible) is true of a thing (modality de re) or true of a proposition (modality de dicto). So here’s a putative example of modality de re:

(4) Louis is possibly five feet tall.

Notice that the “possibly” comes between the copula and the predicate, and as such (4) is predicating ‘possibly five feet tall’ of a thing (res)—namely Louis. Hence, (4) is an instance of modality de re. Now consider

(5) Possibly “Louis is five feet tall.”

Since the “Possibly” is outside of the proposition “Louis is five feet tall”, (5) is attributing a predicate not to a thing (res), but to a proposition (dictum), and hence (5) is an instance of modality de dicto. And of course, since saying “Louis is five feet tall” is equivalent to an assertion, (5) is equivalent to

(5’) “Louis is five feet tall” is possibly true.

On Aristotle’s view, (4) and (5) are interchangeable. Furthermore, since both (4) and (5) are propositions, both are made true by the state of affairs S Louis’ being possibly five feet tall. Since truth depends on reality we can infer S’s obtaining from knowing either (4) and (5), but (4) and (5) bear an asymmetrical dependency relation to S. Namely, S ‘makes’ or ‘necessitates’ the truth of (4) and (5), but the truth of (4) and (5) do not ‘make’ or ‘necessitate’ S’s obtaining.



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