Comment on Mixed Reference: The Great Reductionist Project

Thu, 06 Dec 2012 20:05:06 GMT

I don't think we need this rule. It would make logical truths / tautologies meaningless, inexpressible, or magical. (We shouldn't dive into Wittgensteinian mysticism that readily.)

No, I didn't say that constraining possible worlds is a necessary condition on meaning. I said this:

1) A proposition is meaningful if and only if it is expressible by physics+logic, or merely by logic.

2) If a proposition is expressible by physics+logic, it constrains the possible worlds.

This leaves open the possibility of meaningful, non-world-constraining propositions (e.g. tautologies, such as the claims of logic), only they are not physics+logic expressible, but only logic expressible.

That depends on what you mean by "proposition." The written sentence "the cat is on the mat" could have been ungrammatical or semantically null, like "colorless green ideas sleep furiously."

That's not relevant to my point. I'd be happy to replace it with any proposition we can agree (for the sake of argument) to be meaningful. In fact, my argument will run with an unmeaningful proposition (if such a thing can be said to exist) as well.

On the other hand, if by "proposition" you mean "the specific meaning of a sentence,"

No, this isn't what I mean. By 'proposition' I mean a sentence, considered independently of its particular manifestation in a language. For example, 'Schnee ist weiss' and 'Snow is white' express the same proposition. Saying and writing 'shnee ist weiss' express the same proposition.

This looks like a problem of self-reference, but it's really a problem of essence-selection. When we identify something as 'the same thing' across multiple models or possible worlds...

I didn't understand this. Propositions (as opposed to things which express propositions) are not "in" worlds, and nothing of my argument involved identifying anything across multiple worlds. EY's OP stated that in order for an [empirical] claim to be meaningful, it has to constrain possible worlds, e.g. distinguish those worlds in which it is true from those in which it is false. Since a statement about the meaningfulness of propositions doesn't do this (i.e. it's a priori true or false of all possible worlds), it cannot be an empirical claim.

So I haven't said anything about essence, nor does any part of my argument require reference to essence.

Also, 'GRT' is not in any case logically true; certainly it is not an axiom, and there is no reason to treat it as one.

Agreed, it is not a merely logical claim. Given that it is also not an empirical (i.e. a physics+logic claim), and given my premise (1), which I take EY to hold, then we can conclude that the GRT is meaningless.

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