I think the only way logic has ever made sense to me is as something fixed and external. It is not an invention. There is one logic and there is nothing anyone can do about that, because how can you reason about reasoning?

What are the views of others here about the true nature of logic?

Logic is just there. Whether it's eternal or not is impossible to discern, whether it's internally-constructed or externally valid is impossible to discern. You can't use logic to find the source of logic, just doesn't work. Because logic is a question of conclusions derived from premises, and because when the conclusion is used as a premise in establishing itself the logic is obviously invalid, no circular logical structure can be self-validating.

You can build logic (and other mathematics) from a few very simple conceptual ingredients; the concept of a "thing", the concept of a "relationship" between two "things"; throw in a few axioms and you're off to the races.

The real question is, why is (our patch of) reality endowed with the capacity to accommodate concepts such as "thing" and "relationship" at all?

You don't even know if there is one logic, because how would you make that determination?

its a law of knowledge and nature. no thinking, computation or event can occur outside logical bounds. logic deciphers the inherently impossible from the inherently possible. so by definition, anything illogical is impossible.

I think in this case, existence is more interesting than uniqueness.

logic is eternal by nature. existence depends on logic. to say something could exist illogically at some time in the future is an illogical statemnt in the now and we can dismiss this as impossible.

Logic is not subjective so i dont know what you mean by internally constructed. logic permeates through the knowable universe.

the source of logic is in nature. nature is logical. we define logic to be that which is possible within nature essentially. logic is not circularly defended but rather is necessarily true. There is no means to think otherwise. thinking and logic are intertwined. nature and logic are intertwined. the bounds outside of logic must dispose of nature and knowledge - wat we call illogical.

You're missing an important possibility. Nature might just be approximately logical.

your statement makes no sense. its like people who say there is a possibility we dont exist. how can a possibility exist for non existentce.

Can more than one logic (be known to) coexist without an underlying logic for their interaction?

If you KNOW that, then why don't you know everything?

I agree with you - I also think it applies to mathematical theorems. Although I don't think it's possible to prove that logic is fixed, eternal, transcendent, whatever...I can't comprehend what an illogical universe would even mean.

explain how that is imperative to what i said?

A universe in which not everything is knowable.

are there not different logics?

I was presuming we were taking all possible logics as a set - they all exist independently of whether we've thought of them yet.

I dont think everything is knowable in this universe - but I think it's a logical one.

EDIT: Scratch that, maybe everything is knowable in principle. But that doesnt really help, since if that's right I can't imagine a universe containing some unknowable facts.

You wrote that there is only one kind of logic. Its law is the law of the universe. If you know the law, then you know what is possible and impossible. So if a statement is presented to you, you can figure out whether it's true or false, simply by thinking logically. Theoretically you should be able to figure out the "world-formula". Since you already know how to acquire this world-formula (by simply applying logic), what is it that prevents you from doing so?

if you're presented with a statement you can know its either impossible or possible by virtue of whether it is logical. Some statements can be verified off hand so we can consider them necessarily true rather than just possibly so. On the other hand many statements are hypothetical and are not entirely founded by logic alone. there is no hypothetical nature to something which is logically impossible though.

In computer science, especially AI, there's been a bunch of "logics". But it seems in most of math there's rarely any dispute about what is and isn't logical. I mean someone could post a math puzzle here and there's not going to be much dispute about which logic should be used in deriving the answer.

You can't comprehend it - does that mean you can rule it out?

[1] My statement makes perfect sense. You just don't understand it. [2] It's absolutely nothing like that. [3] Non seqitur.

Now you're completely contradicting yourself. I've got more to say, but why don't you clarify: Do you believe in a perfectly logical universe or don't you (or are open to either possibility)?

I guess no, but it's an interesting topic. Certainly in well known cases of various versions of logic such as:

it's pretty clear they are all subsumed under a single logical umbrella. That's why I said

In what sense, if any, does perfect logic exist?

For practical purposes - since I'm completely incapable of even speculating on "What if this assumption is wrong?"

Of course I dont present it as a proof, but it's another of my "I dont have any real alternative choice, given my limitations, even if I'm wrong. So I'm going to assume I'm right."

If demonstrable self-consistency is necessary for perfect logic, then we can't invent such. The next question is, how much imperfection does logic tolerate? Is an ambiguous condition possible, or does any incompletely derivable, i.e. to some extent arbitrary, proposition in a deductive sequence make void the logicalness of the conclusion?