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What makes mathematics certain knowledge?

Why can mathematical knowledge not be doubted? What gives it the characteristic of certainty? No one has ever coherently answered this question, as far as I am aware. Everyone just seems to take for granted its certainty like they take for granted causality's existence, for instance. Please explain, in full detail, why it is certain. Preferably without utilising formulas or proofs. To wit, referencing formulas or proofs is fine but they cannot be used to elucidate this matter for uneducated individuals.

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Reply 1
Original post by ~MiserableLogic~
Why can mathematical knowledge not be doubted? What gives it the characteristic of certainty? No one has ever coherently answered this question, as far as I am aware. Everyone just seems to take for granted its certainty like they take for granted causality's existence, for instance. Please explain, in full detail, why it is certain. Preferably without utilising formulas or proofs. To wit, referencing formulas or proofs is fine but they cannot be used to elucidate this matter for uneducated individuals.


The only way we can be certain of a particular conjecture is through a mathematical proof, so I'm afraid there's no real way to convey this through words.
Original post by justinawe
The only way we can be certain of a particular conjecture is through a mathematical proof, so I'm afraid there's no real way to convey this through words.


Why is this the case? Is language limited? Is mathematical proof really proof at all?
Reply 3
I think it is fair to say that mathematics is an application of philosophy that provides a rigorous framework for debating problems when phrased in a very particular manner.

As such, to question the veracity of this subject's results in the philosophy forum strikes me as somewhat ironic: if maths is not reliable, then (assuming the formal body of mathematics to be free of mistakes) it will be because its underlying framework, namely philosophy, is similarly unreliable. :s-smilie:

(Philosophy is not my forte, so feel free to correct me on anything I've misinterpreted.)

EDIT: Feel I should clarify that "mistakes" here is meant in the technical sense: "human error" is one of its more vulgar renderings, an error brought about by human imperfection. :yep:
(edited 11 years ago)
Reply 4
Because everything in mathematics is based on something else. We can use basic mathematical axioms to prove simple theorems, and simple theorems to prove complicated theorems, and therefore if the axioms are always true then the rest of mathematics is always true as well.

The proofs themselves are infallible, because they are made up of many smaller steps which, assuming the axioms are true, are also infallible. Therefore, if mathematics can ever be wrong, it will be because the assumptions which underpin it, and the whole of logic and philosophy, are also wrong.
Original post by justinawe
Well, yes, language is limited, in a way. You can't use words to prove something beyond all doubt. When you make an argument through words, you're using logic. While logic is all fine and good, and is an essential skill to have, you can't prove something through logic. There are things that go against logic. You can show that something is highly likely (or unlikely), but that's about the extent of it.

Similarly, you can't prove science through words either. That takes years of experimenting, etc.


You are utterly incorrect. Deductive logic proves something beyond a doubt - it is inescapably true. The second emboldened part is a loose definition of inductive logic. All mathematics may be based on logic - a branch of philosophy. However, I am willing to concede that perhaps I too have assumed logic's certitude as mathematicians assert the certitude of mathematics.

This is an uncomfortable dilemma that has no easy solution. You cannot readily assume a particular method gives you objective proof if you cannot prove it. I cannot conceive of a way in which an infinite regress can be avoided.
Original post by Arbolus
Because everything in mathematics is based on something else. We can use basic mathematical axioms to prove simple theorems, and simple theorems to prove complicated theorems, and therefore if the axioms are always true then the rest of mathematics is always true as well.

The proofs themselves are infallible, because they are made up of many smaller steps which, assuming the axioms are true, are also infallible. Therefore, if mathematics can ever be wrong, it will be because the assumptions which underpin it, and the whole of logic and philosophy, are also wrong.


Perhaps logic and science are incorrect. What makes that an impossibility? Surely it is a valid possibility. Note how I did not state this was your position. I am committing no straw man fallacy. I am merely positing the possibilities.
Reply 7
Using logic to argue that logic is possibly incorrect seems very odd to me.
Reply 8
Original post by ~MiserableLogic~
You are utterly incorrect. Deductive logic proves something beyond a doubt - it is inescapably true. The second emboldened part is a loose definition of inductive logic. All mathematics may be based on logic - a branch of philosophy. However, I am willing to concede that perhaps I too have assumed logic's certitude as mathematicians assert the certitude of mathematics.

This is an uncomfortable dilemma that has no easy solution. You cannot readily assume a particular method gives you objective proof if you cannot prove it. I cannot conceive of a way in which an infinite regress can be avoided.


Sorry, I think you've misunderstood me here. What I was trying to say was that you can't prove something in mathematics with logic through words, not in general.

You must realize though, that mathematics differs from science and philosophy in the sense that it's a human construct, rather than a study of what already exists. You can conclusively prove conjectures within the realm of this human construct.
Original post by james.h
Using logic to argue that logic is possibly incorrect seems very odd to me.


That sounds exactly what Wittgenstein did with philosophy. Paradoxical and marvelous.
Original post by justinawe
Sorry, I think you've misunderstood me here. What I was trying to say was that you can't prove something in mathematics with logic through words, not in general.

You must realize though, that mathematics differs from science and philosophy in the sense that it's a human construct, rather than a study of what already exists. You can conclusively prove conjectures within the realm of this human construct.


Philosophy and science are human constructs too. Perhaps they are internally valid or perhaps not.
Original post by ~MiserableLogic~
Philosophy and science are human constructs too. Perhaps they are internally valid or perhaps not.


While the subjects themselves are human constructs, the things they attempt to prove are not.
Mathematics is a language used to express rather complicated concepts, you'd find it difficult expressing numbers without it. These concepts are certain, mathematics has no affect on certainty just like the english language does not affect what a car is for example, the word just expresses the concept of a car.
Original post by Helloworld_95
Mathematics is a language used to express rather complicated concepts, you'd find it difficult expressing numbers without it. These concepts are certain, mathematics has no affect on certainty just like the english language does not affect what a car is for example, the word just expresses the concept of a car.


Agreed, but you have ignored the main point of my question. Why are these concepts mathematics expresses certain? Is it because they are analytic propositions that are true by their definition, and the predicates contained within the proposition itself? Even then, why do analytic propositions even exist? Is anything ever completely certain?
Original post by ~MiserableLogic~
Why can mathematical knowledge not be doubted? What gives it the characteristic of certainty? No one has ever coherently answered this question, as far as I am aware. Everyone just seems to take for granted its certainty like they take for granted causality's existence, for instance. Please explain, in full detail, why it is certain. Preferably without utilising formulas or proofs. To wit, referencing formulas or proofs is fine but they cannot be used to elucidate this matter for uneducated individuals.


well 1 + 1 = 2, you just can't **** with that. it's true because it's true because it's true. I know you said don't use equations as examples, but that is the simplest example and the principle applies to all of mathematics, no matter how complicated your maths gets. This feels like such a **** explanation.
(edited 11 years ago)
Reply 15
“Mathematics would certainly have not come into existence if one had known from the beginning that there was in nature no exactly straight line, no actual circle, no absolute magnitude.” - Friedrich Nietzsche.
Original post by ~MiserableLogic~
Why can mathematical knowledge not be doubted? What gives it the characteristic of certainty? No one has ever coherently answered this question, as far as I am aware. Everyone just seems to take for granted its certainty like they take for granted causality's existence, for instance. Please explain, in full detail, why it is certain. Preferably without utilising formulas or proofs. To wit, referencing formulas or proofs is fine but they cannot be used to elucidate this matter for uneducated individuals.
I think your implied assumption is correct. There is always doubt. Maths is about as fundamental as subjects get, and its ideas are always derived from a few simple axioms.

But there are axioms that cannot be proven (or disproven) for example, we take a+b=b+a for granted, or even a=a. But we can't prove that axiom, and that is where the uncertainty exists. But it's a pretty nice uncertainty, because we can say that if something does not equal itself then we probably cannot ever know anything (which is a bit of a nasty dichotomy but a convenient one nonetheless.

But likewise, the basic assumption for something like science is that things actually exist (which they may not) and for history is that [history] isn't just a massive conspiracy. The truth is that we can never absolutely know anything


The main thing about maths that is so cool/ strange is how predictive it is. For example, maths predicted the existence of particles, stars and decay patterns before the people who invented that piece of maths realised these things existed/ were possible. i.e. they invented something in ignorance and that invention could predict things they couldn't -which really makes people wonder if maths is transcendent or in some way fundamental to reality. So anyone who has done a lot of maths will realize how creepy it can be. If I haven't explained that well I'm sure someone else can add to it.
Reply 17
Maths is the logic of quantities, it's Analytic and a priori in Kantian terms, it's basically tautological and thus doesn't have to appeal to any empirical 'facts' to verify itself. It's not 'certain knowledge' of anything but itself articulated in various ways, even its knowledge of itself (proofs) are impossible to be sure of since it is never possible to know if one has not missed a mistake in the calculations.
Reply 18
Maths is a closed-loop just like everything else. Everything within the box can be deducted or "proved" based on other contents of the box, so to speak, but once you reach the walls you have to turn around and go back.

If nothing else, anyone who believes that the best human mind is not the very best mind that could ever exist must accept the limitations and fallibility of all systems he has established. I'm sure if there were no humans around then monkeys would think they were pretty damn clever as well, right?
Reply 19
Key thing is mathematicians are extremely careful with definitions. The validity of their proofs essentially relies on their definitions of concerned relevant things. You can only have doubts about things you have no precise/exact idea about.

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