↪Limitless Science Simple: Logic = correct reasoning, that's what it's about, period. — Sam26

Yep. It's what is sayable, not what ought be said.

If you have 1 smartphone and you get 2 more smartphones, you now have 3 smartphones! — Limitless Science

But on the other hand, if you have 1 raindrop and you add 1 more raindrop, you still have only 1 raindrop.

There's a bit of selection in what you talk about.

I belive that 1+2=a bolt of lightning — Limitless Science

An example of what can't be said.

An example of what can't be said. — Banno

He just said it. Just because moving your queen in a square isn't allowed doesn't mean you can't do it.

He just said it. — frank

Just because moving your queen in a square isn't allowed doesn't mean you can't do it. — frank

Just as in performing an illegal move, on ceases to play chess, one fails to make a move - so @Limitless Science failed to say anything.

Trivially, it is possible to adopt the Humpty Dumpty Argument so that any given statement can mean whatever you want it to. Is that the way you want to go, @frank?

Limitless can make the noise; but what has he done, apart from that? What use is "I believe that 1+2=a bolt of lightning"?

...logic is the normative science of how one ought to think if one intends to pursue truth; — aletheist

This is the view I am rejecting, Frank.

Suppose I argued that your view on, say, abortion is wrong because your mother wears army boots.

@aletheist seems to think (and doubtless I am wrong here, but it will serve) that the appropriate reply is something like "one ought not make such conclusions", as if an ad hom argument were a bit rude, subject to the same sort of rejection as "one ought not pick one's nose in public".

I don't think that is enough. It's not enough to say an ad hom argument is a bit rude; it is also plain wrong; the conclusion does not follow from the premise.

Logic does not just set out how we ought speak, but how we can speak. It shows us what sorts of speaking are wrong.

Logic does not just set out how we ought speak, but how we can speak. It shows us what sorts of speaking are wrong. — Banno

You think you are saying something different, but you are not. You just understand "normative" in a narrow ethical sense.

Perhaps.

Some communication falls outside the domain of logic, like "Wow!"

So is it propositional speech that's bounded by logic? If so, that leads to my concern: that logic has something to do with the way the world is.

Is speech a subset of the ways the world works?

So is it propositional speech that's bounded by logic? — frank

Propositional and predicate logic are certainly about propositions...

...that logic has something to do with the way the world is. — frank

Language is about the world; logic is about language; so yes, logic has something to do with the world.

This is the view I am rejecting, Frank.

Suppose I argued that your view on, say, abortion is wrong because your mother wears army boots.

@aletheist seems to think (and doubtless I am wrong here, but it will serve) that the appropriate reply is something like "one ought not make such conclusions", as if an ad hom argument were a bit rude, subject to the same sort of rejection as "one ought not pick one's nose in public".

I don't think that is enough. It's not enough to say an ad hom argument is a bit rude; it is also plain wrong; the conclusion does not follow from the premise.
— Banno

I don't see the distinction you are trying to set up. If something is wrong, you ought not do it, and if you ought not do something, it is because it is wrong. If murder is wrong, you ought not do it. If picking your nose in public is wrong, you ought not do it. There is no division here, between things which are wrong, and things which we ought not do. To imply such a division is to speak nonsense.

Logic does not just set out how we ought speak, but how we can speak. It shows us what sorts of speaking are wrong. — Banno

If and only if it is wrong, one ought not say it. By your principles, you have said here what you cannot say. There is no such thing, by way of contradiction, as what one cannot say, because to identify it as 'the thing which cannot be said' requires that it be said. The sorts of speaking which are wrong are those which we ought not engage in, but this says nothing about our capacity to speak them.

Well, what is logic? If you have 1 smartphone and you get 2 more smartphones, you now have 3 smartphones! That's logic. — Limitless Science

I don't want to be awkward, dismissive or negative, but that's arithmetic, my friend, not logic. :chin:

I don't see the distinction you are trying to set up — Metaphysician Undercover

I find that oddly reassuring...

Here's the problem with the assumption that there is such a thing as what cannot be said. You can assume such a thing, just like I can assume a square circle, but these assumptions don't make these things real.

Logic is developed from the intention of allowing us to know everything. That is the will of the philosopher, the desire to know, and this means everything, without exception; all is to be placed in the realm of knowable. We cannot designate anything as unknowable because then we'd lose the will to know it, being already designated as unknowable. To say that there is something which cannot be said is to say that there is something which cannot be known, and this is contrary to the first principle of philosophy, which is to render everything as knowable.

Therefore nonsense statements, as in the example, are sayable, and also knowable, but they are known as nonsense. And your claim that some things can't be said is also knowable as nonsense.

Language is about the world; logic is about language; so yes, logic has something to do with the world. — Banno

Logic has something to do with propositional language, not all language.

Propositional language is unusual in that it can be spoken by the great third person. In a sense, it is the world's voice.

In the context of this topic (purported normativity of logic), "logic" is not just any abstract system of inference. You could throw together any number of such systems; obviously, they couldn't all be normative. (Normative for what?) The "logic" under consideration is what underlies ordinary deduction. Sometimes people talk of the FOPL in this context, but I think that FOPL can only serve as a proxy. What is (purportedly) normative is an unformalized intuitive rationality, which can be brought out with simple, uncontroversial examples of deduction. Formal logic, such as the modern-day FOPL, aims to capture this intuitive rationality.

The person I was responding to was making the case that even mathematical logic has an inherent normative component to it. Really all I was saying is that there are different senses to "logic" and the norms for correct reasoning is only one sense, it doesn't subsume the others.

I don't think FOPL really captures the intuitive reasoning we're drawn to either, I don't any logic does. That's why people get tripped up by things like the material implication paradoxes or find "ex falso quodlibet" strange, because they don't map onto how we actually reason. FOPL is really, I think, about capturing a certain type of mathematical reasoning, as that was explicitly why Frege created it.

Propositional language is unusual in that it can be spoken by the great third person. In a sense, it is the world's voice. — frank

And...?

Then it would follow that logic informs us about how the world should be. If we come across something illogical, we say "That can't be!" and we go in search of true propositions that straighten the mess out.

If we come across something illogical, we say "That can't be!" and we go in search of true propositions that straighten the mess out. — frank

So when we come across something illogical, we have said it wrong, and look for a way to say it right.

Logic is not telling us how the world is, but how we can talk about the world.

So when we come across something illogical, we have said it wrong, and look for a way to say it right. — Banno

The results of the double slit experiment appear to defy logic. Who misspoke and what did they say?

Appear.

They are described using the appropriate equations. The language was adjusted to the world, not the world to the language.

I don't seriously think you disagree with me on this.

Who misspoke? What did he or she say that was wrong?

Odd. It's your story.

OK.

The results of the double slit experiment appear to defy logic. — frank

https://arxiv.org/pdf/1508.00001.pdf

The article was cited by @StreetlightX in a recent thread.

Have a look at the section on Linear Algebra. Note:

When Heisenberg wrote his famous paper he did not know linear algebra. He had no idea of what a matrix is, and had never previously learned the algorithm for multiplying matrices. He made it up in his effort to un- derstand a puzzling aspect of the physical world. This is pretty evident from his paper. Dirac, in his book, is basically inventing linear algebra in the highly non- rigorous manner of a physicist. After having constructed it and tested its power to describe our world, linear al- gebra appears natural to us. But it didn’t appear so for generations of previous mathematicians.

The language that describes the odd quantum world was created for that purpose.

Logic is not telling us how the world is, but how we can talk about the world. — Banno

‘What we observe is not nature itself, but nature exposed to our method of questioning’ ~ Werner Heisenberg.

What did he mean by that? Do you suppose he thought that he could observe his underpants in his bottom draw only when he was looking for them? That when he was questing for his vest, his underpants were unobservable?

Or do you think his comment was targeting something less mundane?

your remark reminded me of that quotation, especially in the context of discussion of the bafflements of quantum mechanics And no, he’s not talking about underwear, but about the supposed fundamental constituents of matter. I mean, the hope was to discover some such ultimate constituent of matter, but what with the oddities of quantum physics, it wasn’t to be. Get hold of Manjit Kumar’s book, Quantum, it lays it all out.

The language that describes the odd quantum world was created for that purpose. — Banno

That's cool, but it doesn't diminish the fact that the double slit experiment appears to show a contradiction. A mathematical expression of the situation doesn't change that. Quantum theory is made of multiple attempts to explain what's happening, none of them entirely satisfying.

You had said that if we encounter something illogical it's because someone said something wrong. I was trying to identify that wrong statement in the context of quantum experiment.