Did Kepler Die in Misery?

Either he did or he didn't. Suppose I say that he did, and you say that he didn't. We both presuppose, inter alia, that there was a man named 'Kepler.'  Now that proposition that we both presuppose, although entailed both by Kepler died in misery and Kepler did not die in misery is no part of what I assert when I assert that Kepler died in misery.

Why not?

Well, to proceed by reductio, if what I assert when I assert that Kepler died in misery is that (there was a man named 'Kepler' & he died in misery), then what you assert when you contradict  me is that (either there was no man named 'Kepler' or that he did not die in misery). But the latter is not what you assert, and the former is not what I assert.  That is because we take it for granted that there was a man who rejoiced under the name 'Johannes Kepler.'

What I assert is that Kepler died in misery, and what you assert is that Kepler did not die in misery.  But we both presuppose that there was a man named 'Kepler.'  The proposition that we both presuppose, while entailed by what we each assert, is not part of what we each assert.

That, I take it, is Frege's famous argument in Ueber Sinn und Bedeutung.

It seems pretty good to me.

Comments

[The Bad Ostrich]

My previous point remains. If I deny p, I say that p fails to be true.

But if excluded middle holds, every possible state of the world either includes p, or fails to include p. Tertium non datur. But some of the states which exclude p must also include any proposition q presupposed in asserting p.

Thus if I deny that Kepler is an astronomer, I say that it fails to be true that Kepler is an astronomer. But that failure must include the possible state of the world where Kepler does not exist.

Or are you saying that it is impossible to properly negate (i.e. deny) the truth of any proposition?

As for Frege, he clearly accepts excluded middle. In the Kepler case, he holds that if any thought is expressed at all, i.e. if what is expressed is not a ‘mock thought’, then the truth or falsity of what is expressed includes Kepler’s existence, for a true singular thought requires that the singular term has a reference, a Bedeutung.

[The Bad Ostrich]

This is a good paper on Frege, excluded middle and empty (‘fictitious’) names.

[BV]

We may be disagreeing because I think of presupposition as a pragmatic notion and you don't. I'll think about it some more.

[Mark Spahn (West Seneca, NY)]

Libretto:
https://gsarchive.net/mikado/webopera/mk208.html

Performance:
https://www.youtube.com/watch?v=9C9fUX96yqQ

[Damien Spillane]

It seems obvious to me that the object of the proper name cant be a part of the sense of the whole sentence. But i also think Russell has a valid point that imposing a sense between knower and referent presents an epistemic barrier to knowing objects.

I also dont think the reference can "entail" the object since as Armstrong has pointed out, object and true proposition belong in different categories thus entailment cant cross such a barrier.