Freedomain Radio

Today, a fun question was thrown from a stranger. It went something like this: "Prove to me that logic exists. It is an immaterial concept. I can't pull logic out of my fridge."

I would love to discuss it further here, as this particular person (as it turns out) wasn't genuinely interested in an answer or a discussion. It seems that by this person even asking such a question, they are adhering to logic.

I agree that logic doesn't exist, but neither do math or science, so it's not a "knock" on logic, it's just a fact. Logic doens't exist, but it's still valid. He may have different motives for saying "logic does not exist".

What are your thoughts?

 

Logic doesn't exist, except as a tool of human thought (or rather, as a basic expression of the human experience of reality). But so what?

Ironically, indeed, your friend was using logic to argue with you:

1. All valid concepts have a material referent (implied)

2. Logic does not have a material referent (explicit)

C: Therefore, logic is an invalid concept. (implied)

And in doing so, was comically defeating himself.

As for his argument (such that it is): Premise two is flatly false. Logic itself isn't a "concept". It's a process or methodology for validating claims about reality, that is derived from valid concepts. Since the fundamental rules of classical logic are derived from the consistently observed behavioral properties of objects in reality, the rules themselves are valid concepts:

1. The Law of Identity: (A = A) An object is the same as itself.

2. The Law of Non-Contradiction (A != !A): An object cannot be and not be, simultaneously.

3. The Law of Excluded Middle (A | B): Where two statements are contradictory, one must be true and the other must be false.

a fourth rule has been infered from the prior three, in classical logic:

4. The Law of Bivalence (A | !A): Every statement will necessarily either be true, or be false.

At the level of sense perception, all objects will obey these laws. So, the laws that constitute the methodology of classical logic are valid expressions of the behavior of matter at the sense perception level, and are therefore individually valid concepts, and therefore, classical logic is indeed a useful method for understanding reality.

Jil:

Tyff:

Prove that logic exists

ok.

Assume there is not a system that contains truth value for all possible statements.

We do know that this exists:

A -> B

A

B

and

A -> B

!B

!A

Our assumption is false, thus logic do exist.

 

Why do some of you believe existence needs matter?

Why do you believe matter can be proven? Don't you know science got no proofs? They only got evidence and anti-logic. To them something is true until an evidence to the contrary is discovered, and often not even then.

Proof is only a meaningful concept within a logical system and then used only to validate consistency.

If there is something that cannot be proven to exist, matter is our first candidate.

Hi Jil. I'm trying to understand your point. I think you're saying that logical implication can be shown to exist, but that it's not possible to prove that matter exists. Is that correct? Isn't it the case that you can only communicate this to me and the others due to the existence of matter, based on our current understanding?

Jil:

Why do some of you believe existence needs matter?

I think this is definitional.

Something that exists has physical presence.

GregG:

Logic doesn't exist, except as a tool of human thought (or rather, as a basic expression of the human experience of reality). But so what?

Ironically, indeed, your friend was using logic to argue with you:

1. All valid concepts have a material referent (implied)

2. Logic does not have a material referent (explicit)

C: Therefore, logic is an invalid concept. (implied)

And in doing so, was comically defeating himself.

As for his argument (such that it is): Premise two is flatly false. Logic itself isn't a "concept". It's a process or methodology for validating claims about reality, that is derived from valid concepts. Since the fundamental rules of classical logic are derived from the consistently observed behavioral properties of objects in reality, the rules themselves are valid concepts:

1. The Law of Identity: (A = A) An object is the same as itself.

2. The Law of Non-Contradiction (A != !A): An object cannot be and not be, simultaneously.

3. The Law of Excluded Middle (A | B): Where two statements are contradictory, one must be true and the other must be false.

a fourth rule has been infered from the prior three, in classical logic:

4. The Law of Bivalence (A | !A): Every statement will necessarily either be true, or be false.

At the level of sense perception, all objects will obey these laws. So, the laws that constitute the methodology of classical logic are valid expressions of the behavior of matter at the sense perception level, and are therefore individually valid concepts, and therefore, classical logic is indeed a useful method for understanding reality.

 

 

Yeah I also think you're friend was basically right; logic doesn't exist. You can't 'pull it out of your fridge'! 

But it's not important. Objects exist, concepts don't. Everything "thing" is either a physical object or artificial (man-made) concept, as there's no other top category. 

Logic is conceptual, whether one regards it as a process or methodology or whatever. Logic is valid because it is self-validating, i.e. it's tautologous (defined to be such) and resolves to base axioms. We call this definitional agreement 'truth' or 'proof' or whatever. Tautologies aren't "absolutes" in this sense because we can critically reason that they require humans (e.g. a rock doesn't care what a tautology is!). 

Here, I disagree with many here that we "derive" logic "from" reality. Reality is natural (i.e. there just "are" objects, in motion) and must be explained/understood, not proven. Logic is artificial (i.e. man-made) but can be used to prove (verb) or 'demonstrate' by resolving axioms to their definitional foundations. "An object is an object" is itself only a man-made tautology. E.g. there are no laws "in" nature. Rather, laws are generalised descriptions we use to (ideally) help us better understand reality. 

Just my 2c. 

Since we are using logic to construct these very sentences, that seems to be proof of it existing.

How can language be used without adherence to/acceptance of the principles of logic?

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The argument from the person was regarding atheism, and their claim was this: Atheists are not consistent in that they require a 'proof' of god but they accept that logic exists without proof.  They went on to assert that using this 'logic' we would have to accept the existence of god just by talking about him/her/it.
This is absolutely absurd to me because that would mean that just by talking about a pink unicorn with leaves for feet, a pink unicorn with leaves for feet must exist somewhere. Please correct me if I'm wrong.

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Logic is capable of demonstration, this proves it's existence as a descriptor of reality.

Perhaps I needed that precise definition for comprehension.

So, something must have physical presence to exist? Is observable not a proof of something existing?

GregG:

Logic doesn't exist, except as a tool of human thought (or rather, as a basic expression of the human experience of reality). But so what?

Ironically, indeed, your friend was using logic to argue with you:

1. All valid concepts have a material referent (implied)

2. Logic does not have a material referent (explicit)

C: Therefore, logic is an invalid concept. (implied)

And in doing so, was comically defeating himself.

As for his argument (such that it is): Premise two is flatly false. Logic itself isn't a "concept". It's a process or methodology for validating claims about reality, that is derived from valid concepts. Since the fundamental rules of classical logic are derived from the consistently observed behavioral properties of objects in reality, the rules themselves are valid concepts:

1. The Law of Identity: (A = A) An object is the same as itself.

2. The Law of Non-Contradiction (A != !A): An object cannot be and not be, simultaneously.

3. The Law of Excluded Middle (A | B): Where two statements are contradictory, one must be true and the other must be false.

a fourth rule has been infered from the prior three, in classical logic:

4. The Law of Bivalence (A | !A): Every statement will necessarily either be true, or be false.

At the level of sense perception, all objects will obey these laws. So, the laws that constitute the methodology of classical logic are valid expressions of the behavior of matter at the sense perception level, and are therefore individually valid concepts, and therefore, classical logic is indeed a useful method for understanding reality.

This is helpful. Thank you.

Jil:

Have you seen incoherent rant sometimes?

On what basis are you calling anything incoherent?