"is true" and "ought to"

Here's something I believe to be correct, but I'm not positive.

I took a course on Frege last year with Prof Goldfarb, and we discussed Frege's views on the predicate "is true." This predicate/property seems to be unlike any other property. Usually, when a predicate (concept) is tagged onto some subject (object) there is information conveyed. For example, "The table" might be any color in the world--red, blue, murple, etc. When I say, "The table is blue" I've really added some information that wasn't there before. Now, consider the property "is true" added on to some sentence. For example, consider the sentence "The table is blue". That sentence seems to tell me what color the table is. Now, apply the predicate "is true", and you get " 'The table is blue' is true." This seems to tell me that "The table is blue" is true. But that doesn't really add any information to the first sentence! Of course, if I asserted "The table is blue" seriously, I meant for you to think that it was true. So what does "is true" add? Seemingly nothing.

This is why Frege writes (in "Thought"), "The reference of the world 'true' seems to be altogether sui generis. May we not be dealing here with something which cannot be called a property in the ordinary sense at all? ... I will begin by expressing myself in accordance with ordinary usage, as if truth were a property until some more appropriate way of speaking is found." It sure sounds like Frege is saying that "is true" isn't a normal property. (Goldfarb told us that this point is controversial, but I can only see one side of it in Frege.)

So, if "is true" isn't a real property--in the sense that it's unlike every other property because it doesn't add any information, doesn't ascribe anything to the object or subject of the sentence--then what is its function in a sentence? As far as I can tell, "is true" basically serves to clarify that you are truly asserting the sentence. Allow me to clarify. We can all imagine contexts in which we could utter the words "The table is blue" but not mean for them to be taken seriously. For example, we could just be playing around with words. We could be describing a fiction, a way that the table could be but actually isn't. In all these cases we don't mean to state a fact or to make an objective assertion, we don't mean to say something that can be true. So, my sense is that "is true" serves to clarify that you're truly asserting a sentence with the intent for it to be taken objectivley and seriously. You want it to be objective--either true or false.

Now, let me shift gears for a minute. Colyvan, in his book in the Indispensability argument, is careful to distinguish between two different arguments. The first of them has as its conclusion "We ought to believe that numbers exist." The second of them has as its conclusion "Numbers exist." He thinks that the first one is better than the second, because the second is more controversial. What's the difference? The first is a statement about what we should believe, but it's careful to avoid talking about the world. Why? Well, because you might doubt the strength of your evidence. But then are you really justified in beliving that numbers exist in the first place? I consider this to be an instance of something that Michael Resnick mentions in his article on this: there's a kind of incoherence in saying "I'm justified in believing X, but I don't think X is true." Either you have evidence--and you're justified--or you don't. Yes, of course, there are levels of certainty, and everyting is revisable. But if you're justified in believing X--whatever it takes to make you justified--then certainly you should believe that numbers exist.

I submit that there is no difference between the conclusion of an argument that reads "Numbers exist" and one that concludes "We ought to believe that numbers exist". This is because "We ought" just means that you're making a normative statement, that you're asserting something normatively. But if the sentence "numbers exist" comes at the end of some argument, then we KNOW that you're asserting the sentence normatively, and there isn't any difference between them. This is parallel to the picture I described above for "is true." "I ought" or "you ought" or "one ought" just indicates that a normative statement has been made, completely parallel to the funciton of "is true." One more pass at it: to say "I ought to believe in p and not p" is just as irrational as to say "p is true and not p." (I was a little bit sloppy here. There's a bit of room for doubt, because we often say "I should believe that X, but I just can't bring myself to believe it. But that just means that you're not able to be rational for whateve reason. What's at issue is whether it would be rational to say "I ought but don't.")

If this picture if right, then certainly there's no point in differentiating between the two types of arguments. One is just a wussier version of the other.

Why would "We ought" and "is true" have similar functions? Likely because normativity is built into objective claims. When I make an assertion about the world I am saying "You ought to believe that the world is this way." So truth might be a kind of normativity. That's pure speculation.