If "I agree that there is a cup" and "there is a cup" mean different things (which they do under some metaphysical systems) then it does (and so could be true) — Michael

Not necessarily.

"I agree that there is a cup" refers to assent to (someone's) factual statement "there is a cup".
"there isn't a cup" refers to a factual statement.

The former tells that not only do I think that there is a cup, but I also agree with someone over this - we share the same thought.

The statement is contradictory if "there is a cup" and "there isn't a cup" refer to the same object at the same place/time. So in this case, even if I grant that agreement and truth are different (agreement doesn't require to be based on truth, we can agree on something false, and truth doesn't require agreement to be true) it follows that the statement is contradictory - because agreement IMPLIES I think it is true - which contradicts the later part of the sentence where belief to the contrary is expressed.

Thus: "I agree that there is a cup" means what "there is a cup" does, and more.

I'm really not sure how to understand that. If "I agree that there is a cup" and "there is a cup" mean different things then the negation of the latter ("there isn't a cup") doesn't contradict the former.

I'm really not sure how to understand that. If "I agree that there is a cup" and "there is a cup" mean different things then the negation of the latter ("there isn't a cup") doesn't contradict the former. — Michael

Read my correction. "I agree that there is a cup" means what "there is a cup" means. It also means something more than just that. Do you not understand this?

"I agree that there is a cup" = Meaning 1 + Meaning 2
Meaning 1: I think there is a cup
Meaning 2: Me and someone else think the same thing

"There is a cup" = Meaning 1
Meaning 1: I think there is a cup.

Read my correction. "I agree that there is a cup" means what "there is a cup" means. — Agustino

So you're agreeing with the second suggestion in my opening post?

"But it could also be argued that the statements "I agree that there is a cup" and "there is a cup" are doing the same thing – asserting that there is a cup – and so mean the same thing, making the first sentence a contradiction."

It also means something more than just that. Do you not understand this?

No, I don't. How can it mean the same thing and more than just that? Are you saying that "there is a cup" has two different meanings?

Got it now. You were talking about the sentence "I agree that there is a cup".

"There is a cup" = Meaning 1
Meaning 1: I think there is a cup.

So "there is a cup" and "I think there is a cup" mean the same thing? Then there is a cup iff I think there is a cup.

So "there is a cup" and "I think there is a cup" mean the same thing? Then there is a cup iff I think there is a cup. — Michael

When you make that statement "there is a cup" it means "I think there is a cup". The statement "there is a cup" itself is purely factual and independent of what you think, but obviously that isn't the case when you make it - it doesn't have that meaning. I mean there are difficulties because you could be for example hallucinating a cup, etc.

When you make that statement "there is a cup" it means "I think there is a cup". The statement "there is a cup" itself is purely factual and independent of what you think, but obviously that isn't the case when you make it - it doesn't have that meaning. I mean there are difficulties because you could be for example hallucinating a cup, etc. — Agustino

So whenever we say "there is a cup" we mean "I think there is a cup"? Then how can we ever (correctly) claim that "there is a cup" is a factual statement that is independent of what we think? Because in making this claim we're claiming that "I think there is a cup" is a factual statement that is independent of what we think.

I think the difference is a first-person/third-person thing.

If you say 'there is a cup,' under normal cup-being-there circumstances, you mean 'there is a cup.' You generally don't mean 'I think there is a cup' unless you're also engaged in second order reflections on your own beliefs, on the nature of knowledge, etc.

If someone asks you if they can go to the kitchen and get some water, there's an obvious difference in meaning between saying 'there's a cup' and 'I think there's a cup.'

If someone observing from afar - who has no interest in the situation, who doesn't need a cup or need to know whether there's a cup for any personal reasons - were to describe what's happening when a person says 'there's a cup,' they might then say something like oh 'he thinks there's a cup.' Though even then, they'd only say that if they were analyzing the statement in a certain way.

I also agree with Agustino that "I agree there is a cup" is different than saying 'there is a cup.' That's because the addition of "I agree" makes it performative. To say "I agree that x" is to enact that agreement. Of course it would be nonsense to say 'I agree that x' and 'not-x'. It would also be nonsensical to say both 'whales eat krill' & 'whales don't exist.' But 'whales eat krill' and 'whales exist' don't mean the same thing. Something can logically entail something else, such that the falsity of the latter guarantees the falsity of the former, but that doesn't mean they're the same thing.

How silly of me. This is more-or-less Moore's paradox. Also related (and perhaps more so) is the preface paradox.

So whenever we say "there is a cup" we mean "I think there is a cup"? Then how can we ever (correctly) claim that "there is a cup" is a factual statement that is independent of what we think? Because in making this claim we're claiming that "I think there is a cup" is a factual statement that is independent of what we think. — Michael

Not exactly, but in discourse we treat each other's affirmations ("There is a cup") as if they were "The other person think there is a cup". Of course we treat our own affirmations as if they were really true (at least most people do). I would advise on some caution though. When someone claims I remembered something incorrectly, or I didn't see something right, I agree very easily with them and admit that I may be wrong - I doubt my perceptions quite quickly - perhaps too quickly.

I think the difference is not something that can be said as Wittgenstein put it. It can only be shown. For example, you walk in the room and tell me: "there is a cup on your nightstand". I will not take it to mean "Michael thinks there is a cup on my nightstand" - I will take it to mean "there is a cup on my nightstand". But if you walk in the room, and you say "there is a cup on your nightstand" and Emily at that point looks up and says "no there isn't a cup there" - then I will treat it as "Michael thinks there is a cup on my nightstand" and associate it with "There may be a cup on the nightstand". Meaning is use, and it depends on context, and the unspoken "rules" of interpretation.

Regardless, my affirmation still stands if we remove the "I think" from both meanings.

"I agree that there is a cup" = Meaning 1 + Meaning 2
Meaning 1: There is a cup
Meaning 2: Me and someone else think the same thing

"There is a cup" = Meaning 1
Meaning 1: There is a cup

Does the above make sense? — Michael

That depends on what you mean by 'makes sense.' In lay terms when we talk about things not making sense, any number of theoretical analyses might be called for. It might not make sense because it's word salad, syntactically ill-formed, even if the semantic interpretation is recoverable ('Went the to store I'). It might not make sense because while syntactically well-formed and semantically interpretable, it conflicts with ingrained world knowledge ('the bus ate the children') or results in category errors ('blue is the smartest color').

As for as the intelligibility of your sentence, it doesn't seem to differ in kind from 'there is a cup and there isn't a cup.' Since this is a contradiction, whatever nonsensicality the agreement ascription has is likely reducible somehow to the nonsensicality of contradictions generally. What nonsensicality is that? It's syntactically and semantically well-formed, abut it conflicts not so much with world knowledge but with intensional or cross-world knowledge: due to the interpretation, any competent speaker will know that in any situation it expresses a falsehood. This is a kind of 'countersense' or 'absurdity,' but that doesn't mean there's anything wrong with the sentence as a linguistic object. It might never be appropriately assertable in canonical speech contexts, where the point is to assert something true, and it'll never be true.

Likewise, why would any competent speaker ever agree to a contradiction? To agree with a proposition is to count it true on the presupposition that someone else does as well. But why count true what your semantic competence should tell you can never be true? There is nothing wrong with the sentence, but saying it will pretty much always be a bad idea.

If you structure the sentence with 'agree' only taking scope over the first conjunct, I agree [there is a cup], and (but) there isn't a cup, then the result is a Moorean paradox, in the sense that it causes no contradiction but is systematically infelicitous to assert. That there is no semantic problem here can be seen from the fact that such things can be supposed, attributed to other people, attributed to oneself in the past, or put in antecedents of conditionals:

-Suppose I agree there's a cup, but there isn't one.
-You agree there is a cup, but there isn't one.
-I agreed there was a cup, but there wasn't one.
-If I agree there is a cup but there isn't one, then I'm wrong.

It's only when it's stated in the first person present that a problem arises:

#I agree there is a cup, but there isn't one.

This shows that the issue is a pragmatic one governing norms of assertion. You commit to believing what you assert, and agreement commits to belief. So you're stating there isn't a cup, which commits you to believing that, but then saying that you agree there is one, which entails you believe the opposite of what you just committed to. This problem doesn't arise in the other contexts above.

So if I understand you correctly, you're saying that although the sentence itself is coherent and possibly true, it cannot be asserted with honesty? The issue isn't with the statement but with the act of stating it?

Yeah, the proposition expressed can definitely be true, which you can see if you ascribe it to someone else, yourself in the past, suppose it, etc. But commitment to belief that attends assertion makes it a systematically bad thing to assert as a speech act. You can say it, but not as a stand-alone speech act, meaning the speech act and not the sentence is bad. It's a pragmatic problem, not a semantic one.

That certainly makes sense.

Apologies beforehand, but I don't get it. If there's a cup, then there's a cup. If you agree that Trump is the worst candidate for office, then you believe that Trump is the worst candidate for office. Agreement necessitates belief.

If you agree that Trump is the worst candidate for office, then you believe that Trump is the worst candidate for office. — darthbarracuda

Yes, but that I agree (or believe) that Trump is the worst candidate for office is not that Trump is the worst candidate for office (or is it?). Because of this it should be sensible to say "I agree (or believe) that X and not X". Neither part contradicts the other. That's Moore's paradox.

If "not X and Michael believes X" makes sense then it makes sense even if Michael says it (even if it doesn't make sense for Michael to say it).

Augustino has been torturing me, and I have been obliged to agree that there is a cup although there is no cup. ( Don't tell him I said that last bit though.)

Ceci n'est pas une phrase. (Quantum logicians need not apply)

"I agree that there is a cup and there isn't a cup."

Does the above make sense? — Michael

It can do. One can state agreement that there is a cup, even if one doesn't believe that there is a cup, and even if there isn't a cup. There are many possible reasons for stating agreement, and, to use your example, the belief that there is a cup is just one of them.

"I agree with you that there is a cup, (even though there isn't a cup)."

We could state our agreement that Donald Trump is the best candidate for President of the United States of America, even though we both know that he isn't, because we would be stating agreement for some other reason. Perhaps just for fun or so that it appears as though we have something in common or for money or for any of a number of reasons.

Alternatively, it could be interpreted as agreement to both a statement and its contrary - which is understandable, in that we know what it says, but the statement that is being agreed to is false and illogical:

"I agree that there both is and is not a cup."

Or

"I agree: there both is and is not a cup."

If "I agree that there is a cup" and "there is a cup" mean different things... — Michael

They do.

But it could also be argued that the statements "I agree that there is a cup" and "there is a cup" are doing the same thing – asserting that there is a cup — Michael

But they're not. The former additionally expresses agreement. It's not like expressing agreement is meaningless and redundant, thereby making the two statements equivalent in meaning.