Is logic undoubtable? What can we know for certain?

Towers

I couldn’t find another topic about this, I hope I’m not redundant

My question for you is: can we be certain that the laws of logic are valid? Or is logic to be taken as an absolute a priori?
What I am trying to say is that many ethical beliefs can be logically deemed ideas taken as true without any rational thinking (if I say that all man are equals, I am expressing essentially a belief and not a certain thing) and that, i believe, is the base of every kind of relativism (we cannot know for certain that killing is wrong or that helping people is good, we just believe they are) yet, whenever we think or we doubt something we cannot do it without the laws of logic.
Can we, so to say, ”trust” the laws of logic? Are they absolute or rather just to be taken as if they were?

And my second question for you is: can absolute relativism be logically acceptable?
Taking the laws of logic as true, is it possible to consider everything relative without contradiction? I mean, if I say that ”everything is relative”, then the fact that ”everything is relative” is not relative anymore, it is absolute, and if I say that even that is relative, so that ”even that everything is relative is to be considered as relative” I’m still considering the relativism of the relativism of everything as absolute, thus contradicting myself.

I sincerely hope you understand my questions, I tried my best and I’m not a native speaker.
I’ll be waiting for your answers

Have a nice day

View Answer

TheMadFool

The issue you're raising has no simple answer.

My opinion is logic isn't perfect. It can't fully describe our experience. I think it's safe to say that classical logic ran into trouble in quantum physics. There are, I daresay, a lot of weird (read ''illogical'') stuff going on in the quantum world. With classical logic only we'd be forced to deny many quantum-level ''facts''.

This is a very difficult position for those who must face it. Do we reject fundamental laws of logic like the law of noncontradiction or do we reject the results of quantum experiments?

Logic still needs a lot of work. Perhaps there is no ONE system of logic that'll work in ALL situations. We may need to develop different systems for different situations or issues. I think that's the general direction of efforts in logic.

Also, your paradox about ''everything is relative'' applies here because you seek evidence that will show you that you can trust logic. Isn't that already trusting logic? I mean to ask for justification for logic you're pre-assuming logic to be jusified.

Id you were to deny logic any trust then even that would require justification. It's a vicious cycle.

Terrapin Station

Certainty: see Rene Descartes' Meditations

Logic: Is an extrapolation of how we think about relations; there are different species of logics, with incompatible axioms, etc.

Ethics: ethical foundations have nothing to do with logic and ethical utterances are not true or false.

Inis

Ethics: ethical foundations have nothing to do with logic and ethical utterances are not true or false. — Terrapin Station

Is it not true that, in order to achieve scientific progress, and knowledge in general, that a certain morality is required? A society cannot progress towards the truth unless they value it, and are open to change and willing to subject their ideas to criticism.

If you value truth, then there are objectively better ways to act.

Towers

↪TheMadFool

Well for the second question I assumed classical logic was reliable and went on with it, I was aware of it, I was not trying to prove it right or anything.

As for the other subject I think you raise an interesting issue, since you said that classical logic ran into trouble because of quantum experiments results (and I assume you are referring to the particle wave duality and its implications) I want to ask you: do you think that logic (and if you want philosophy itself) should submit to scientific results?
Because I think there would be a bit of stuff to deal with.
I’m referring to the fact that science holds many philosophical ideas as true and proceeds without explaining them, for example science believes there is something outside thought, which, philosophically, is not certain at all. So, the implications of scientific experiments, which rely on philosophical concepts, can be used to change those philosophical concepts?

P.S. Don’t worry, I’m not trying to prove quantum physics wrong, I’m just asking.

Towers

↪Terrapin Station

The fact that ethical fundations have nothing to with logic might be arguable but I agree with you.
Yet, I sincerely don’t understand what your point is with the different and incompatible logics.

Towers

↪Inis

But again, what is truth and what is better?
Besides, for scientific progress (which I believe you think as ”good”) a lot of things we generally don’t see as moral has been done.

Inis

But again, what is truth and what is better?
Besides, for scientific progress (which I believe you think as ”good”) a lot of things we generally don’t see as moral has been done. — Towers

If you value knowledge, then only certain moral systems will support that value. Are they objectively good? I'm not sure that question is answerable. Are they objectively better? They are, in exactly the same way that General Relativity is better than Aristotle's theory of gravity.

Towers

↪Inis

What you are saying makes sense, but what is knowledge? What can you know surely?
I don't know if you are familiar with Rene Descartes but I based my questions mostly on his solutions.

But if you were trying to say that if you want X you need to do Y, then I agree with you.

P.S. You mentioned gravity, but what if there is nothing outside thoughts and everything we experience is an illusion? What if I don't exist?
Aristotle and Einstein would have wasted their time on an illusion

BrianW

can we be certain that the laws of logic are valid? Or is logic to be taken as an absolute a priori? — Towers

Depends on what is meant by logic.
If by logic we mean rationale or reason then it becomes subjective and dependent on perspective. This is because we can rationalize or reason out anything depending on the factors we give precedence to over others (priority), or in accordance with how we evaluate significance and meaning.

If by logic we mean the principles which govern the working of reality, then we refer to laws which are absolute in their unity and harmony and which cannot be transcended (altered or undone) by any phenomena because they are strict and unyielding in their domains.

BrianW

P.S. You mentioned gravity, but what if there is nothing outside thoughts and everything we experience is an illusion? What if I don't exist? — Towers

Then, where would the thoughts and illusions exist?

Mayor of Simpleton

My question for you is: can we be certain that the laws of logic are valid? — Towers

As BrianW stated above:

What do you mean by logic?

It has various incarnations such as:

Syllogistic logic
Propositional logic
Predicate logic
Modal logic
Informal reasoning and dialectic
Mathematical logic
Philosophical logic
Computational logic
Non-classical logic

I find it a bit difficult to handle each of these fields of logic as a one size fits all general notion called logic.

Meow!

G

Towers

↪BrianW

You mean the laws of nature right?
Even if I were to look at reality with the eye of an empirist or a materialist I'd still have a hard time calling "unyielding" quantum physics.
But by logic I was referring to classical logic, Aristotle's laws, for example, A is A, A is not B and there is not a third option, tertium non datur, and the recent addings like De Morgan's work.

Should have been more precise then, my bad

Towers

↪BrianW

Elsewhere, I'm just supposing, you see with the eyes of an empirist or a materialist, Plato's ideas don't exist in a material sense

Towers

↪Mayor of Simpleton

Yes you are right, I should have been more clear, I was referring to classical logic from Aristotle onwards, so I guess Syllogistic logic and friends, like I wrote to BrianW

Inis

What you are saying makes sense, but what is knowledge? What can you know surely?
I don't know if you are familiar with Rene Descartes but I based my questions mostly on his solutions. — Towers

Certainty in knowledge is impossible, worthless, and damaging. What you are seeking is an authority, to certify certain truths. There is no such thing.

Towers

↪Inis

But yours are certainties, you are certain that there is no certainty, how is it possible? How do you know?

Towers

↪Inis

My point is: is it logical to say that absolute certainty is absolutely uncertain or even impossible?
We are saying that A is A and also B, but it cannot be anything else

BrianW

You mean the laws of nature right? — Towers

Not explicitly. I used "the principles which govern the working of reality" because reality applies to everything that is, regardless of conditioning.

I believe the laws of logic as derived by Aristotle to be valid and comprehensive. They are:

Plato's ideas don't exist in a material sense — Towers

Then in what sense do they exist, and how do they relate to a Plato who also has a material presence?
I believe the significance of the materiality or immateriality of objects/subjects is dependent on their practical value. That practical value can make immaterial factors to be empirical and material factors to be theoretical. For me, the conditioning does not exclude the unity of everything just like in our lives we employ both the material and immaterial.

Towers

↪BrianW

So you are sure that there is a material or practical level of existence?
How do you know that?

Mayor of Simpleton

↪Towers

So basically it sounds as if you are concered with how we have such things as Modus ponens and other valid arguments (inference)?

If so, in this case I'd say you can use a truth table to justify it.

Modus ponens p → q

The other rules of inference follow that same sort of means of validation. It's not all too difficult to justify them as reliable tools with which one can infer conclusions and such. Perhaps the application of these tools of logic is another kettle of fish.

Meow!

G

Towers

↪BrianW

I was wondering if that logic can be doubted, if I correctly use it in syllogism for example, will I get the most correct conclusion or one of many possible and neither correct nor wrong conclusions?

BrianW

So you are sure that there is a material or practical level of existence?
How do you know that? — Towers

By practical I mean having utility or being functional, and both the material and immaterial have proved to be that.

I was wondering if that logic can be doubted, if I correctly use it in syllogism for example, will I get the most correct conclusion or one of many possible and neither correct nor wrong conclusions? — Towers

I find that logic to work in all cases.

Mayor of Simpleton

While I'm thinking of it you can also use Venn Diagrams in the effort to illustrate and validate (also defend - defeat) Categorical Syllogisms. https://philosophy.lander.edu/logic/syll_venn.html

Meow!

G

Josh Alfred

↪Towers

As far as I know the laws of logic, the rules of syllogisms, an introduction in deduction and induction are not taught in primary school, and because of this I think a lot of people don't know how to reason or use logic well.

Personally, I run into problems that logic has. But if you know modus ponus, for example, you can reduce the errors in your logical thought processes. If you didn't know them however, logic could lead you into confusion and conclusions that are not substantiated by deductive validation.

I really do think if we gave primary school classes on logic there would be less religious participation. This is of course a hypothesis, a logical argument on its own. Our logic skills correlated with religiosity? I digress.

I did enjoy reading the ideas of some people here about non-classical logic. I will not get into that in this reply.

Mayor of Simpleton

As far as I know the laws of logic, the rules of syllogisms, an introduction in deduction and induction are not taught in primary school, and because of this I think a lot of people don't know how to reason or use logic well. — Josh Alfred

Just imagine how different things would be if indeed these were taught and we included an understanding of logical fallacies (such as argumentum ad passiones or hasty generalizations)?

I somehow think Facebook and Reddit would be far less of an addictive frustrating entertainment. ;)

Meow!

G

Towers

↪BrianW

Still, you didn't answer, you believe that things exist in both material and immaterial ways, right?

Anyway the A is A and not B is a bit of a deal with Quantum physics, like ThaMadFool said before, how do we fix it?

BrianW

Still, you didn't answer, you believe that things exist in both material and immaterial ways, right? — Towers

Right.

Anyway the A is A and not B is a bit of a deal with Quantum physics, like ThaMadFool said before, how do we fix it? — Towers

I haven't met any deal to speak of.

Deleted User

This user has been deleted and all their posts removed.

Towers

↪BrianW

Well there is a bit of A is A but also B but not at the same time, I don't have the preparation to explain it better, I'm sorry, I studied it but my explanation are not exhaustive.

Towers

↪tim wood

Well it is clear enough, I understand what you mean but I can't say I agree completely.
My point is that in everyday life we use logic to understand relations of events, the road's wet so it must've rained and if it is very cold outside lakes will freeze. So, if we are presented a relation of events that does not follow that pattern we call it wrong, if you touch ice you do not get burned (I realize these are terrible examples but they'll do)
But you can never use logic on logic, to prove it right nor wrong so can we trust it? And how do we know? Is logic the correct instrument to measure the world around me, if it exists?
What are the limits of it?

My second point, the one you didn't understand was only about trusting logic as an absolute tool a priori, without explanation, as I believe that we cannot express thoughts without one absolute at least.

This is very confused, sorry, I hope you understand

Is logic undoubtable? What can we know for certain?

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