Question

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KDU

Logic is circular therefore it is invalid

This is an argument I have encountered several times and I always find it difficult to respond to.

P1: Logic is required to justify logic

P2: Using logic to justify logic is circular reasoning

P3: Circular reasoning is invalid

C: Logic is invalid (or 'broken')

Usually, the person making the argument then goes on to claim that faith is no worse than logic since logic is invalid/broken. For example: "You can't justify logic, so why do I have to justify my belief in XYZ?"

The obvious rebuttal would be to point out that they already presupposed logic in order to refute logic. However, one counter argument is that the only reason they used logic is to show that it is a self-refuting system. 

Any advice on how to approach these sorts of arguments? Is it even worth arguing with someone that rejects logic from the start?

Thanks

asked on Tuesday, Jun 28, 2022 09:52:07 PM by KDU

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Jason Mathias
3

Ironically they are using logic to try and invalidate logic. 

answered on Tuesday, Jun 28, 2022 10:51:00 PM by Jason Mathias

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TrappedPrior (RotE)
2

It's worth pointing out that circular reasoning is only problematic when the circles are insufficiently large to exchange meaningful information. This is because arguably, all arguments are circular, as they all converge on first principles or axioms. If the circle is big enough, though, it will attempt to adequately justify its conclusions with evidenced, supporting premises.

In addition, as Jason Mathias points out, anyone who says this is using logic to try and invalidate logic - this is the stolen concept fallacy.

Further, the argument itself can be made circular:

Logic is required to justify logic -> Using logic to justify logic is circular reasoning -> circular reasoning is invalid -> logic is invalid, because -> logic is required to justify logic...

answered on Wednesday, Jun 29, 2022 09:54:12 AM by TrappedPrior (RotE)

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Petra Liverani
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When they say that logic is required to justify logic you could ask why it's required. I'm not sure what the answer to that question would be.

answered on Wednesday, Jun 29, 2022 08:00:34 AM by Petra Liverani

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Dr. Richard
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Yes, this is the Fallacy of the Stolen concept, which I define somewhat differently than Bo. I define a concept as “stolen” when one asserts a concept while denying or ignoring its epistemological or genetic roots. 

Can one posit a concept while denying the concept’s prior roots? Logically, of course, one cannot do this. For example, one cannot discuss the concept of an orphan while denying the concept of parents.

But there are other errors involved here. 

Understanding of an axiom and the definition of logic. For simplification, my definition of an axiom is a proposition that defeats its opponents because they have to use it in any attempt to deny it. 

Logic itself is the focus of the discussion. Therefore, it must be explicitly defined.  

The term “logic” is used quite often, but usually not in its technical sense. Logic, strictly speaking, is the science or study of how to evaluate arguments and reasoning. Logic is what allows us to distinguish correct reasoning from poor reasoning. Logic is important because it helps us reason correctly —  without correct reasoning, we don’t have a viable means for knowing the truth or arriving at sound beliefs. Restated, and as a good working definition, I say logic is the correct identification of the facts of reality.

So, applied here, to claim “Logic is required to justify logic” defeats itself because the proponent must use it in any attempt to deny it. 

While logic appears to be concerned solely with the process of reasoning, it is ultimately the result of that reasoning which is the purpose of reason. For example, logic allows you to learn that arsenic and soda is different from a soft drink, though both taste sweet.

answered on Wednesday, Jun 29, 2022 11:50:20 AM by Dr. Richard

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Jorge
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I don't think that logic is required to justify logic. As somebody already said (what I remember they said), axioms are valid to use in systems. The branch of study is the system and the axioms. 

Example: The associative law of addition is needed to perform arithmetic. Would we really say that mathematics is required to justify the associative law of addition? 

I think that there's a play of words with premise 1. By requiring logic to justify logic, what we mean is that rules of inference are needed to perform deductions. Would we really say that logic is required to justify the rules of inference? 

Then there is a confusion between the name of the branch of study and the axioms they're used to perform the operations that the system is meant to allow. 

Example: Modus ponens is a rule of inference found in logic. Therefore, modus ponens is logic. 

This would be appeal to definition.

1. The dictionary definition of "logic" does not distinguish the branch of study with the rules of inference.

C. Therefore, there is no distinction between the name of the branch with the rules.

Notice how premise 2 depends on premise 1. The reasoning becomes circular only if we insist that the name of the branch is the same as the rules that we use. 

answered on Wednesday, Jun 29, 2022 11:22:31 PM by Jorge

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Trevor Folley
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If it is circular reasoning to use logic to justify the logic then so is using faith to justify faith.

This negates both - which might be their intention.

If, however, they are using logic to justify faith, I assume they would be okay with using faith to justify logic.

It would be helpful to know whether, when they refer to logic, they mean,

  1. a priori reasoning, independent of experience (deductive)
  2. a posteriori reasoning, relying on experience/evidence (inductive)
  3. both

If it is purely a priori reasoning then you can appeal to empirical evidence for the efficacy of deductive reasoning.

The problem is that it is impossible to make sense of evidence without using some deduction.

If they are denying the validity of any form of deduction then communication becomes impossible which makes the conversation (quite literally) meaningless.

answered on Thursday, Jun 30, 2022 06:50:14 AM by Trevor Folley

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TrappedPrior (RotE) writes:

Good point and similar to Dr Richard. Denying logic would appear to require the use of logic, making the proposition useless.

posted on Thursday, Jun 30, 2022 02:09:09 PM
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Jorge writes:

If we appeal to empirical evidence for the efficacy of deductive reasoning, wouldn't we run into the problem of induction? 

I think that if we re-phrase premise 1 as "rules of logic are needed to justify rules of logic," then it has merit.

posted on Thursday, Jun 30, 2022 10:50:44 PM
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Trevor Folley writes:

[To Jorge]

Your absolutely right. The problem of induction is always with us. I guess it depends on whether the problem of induction is a problem for the person positing the argument to KDU.

It would be interesting to see whether they draw upon experience to back up their faith.

If they proclaim both a priori and a posteriori logic as false then the conversation becomes merely an exchange of sounds, without meaning.

The simple statement, "The cat sat on the mat" requires the use of sets (e.g. the set, cats) and we need logic to determine whether something belongs to that set.

Your restatement of P1 unpacks 'logic' helpfully. It is difficult to get away from the circularity in both positions.
If the rules of logic work then they can show that the rules of logic work
If faith is enough then we can be confident that faith is enough

Interestingly, it seems that both sides of the argument might be leaning of the stolen concept fallacy.

One side has faith in logic and the other thinks faith makes sense.

Wittgenstein was troubled with a similar dilemma when he wrote Tractatus Logico-Philosophicus. He explores the limits of philosophy and how language can be meaningful. He indicates that true propositions of logic are always true (by definition) and therefore tautologies. The truth-value of logical propositions is independent of how things are in the world and so, Wittgenstein proposes, they say nothing.

He says that he has used logic to elucidate truth but once the truth has been elucidated we see logical propositions as non-sensical...and we will "see the world aright."

My propositions serve as elucidations in the following way: anyone who understands me eventually recognises them as nonsensical, when he has used them - as steps - to climb up beyond them. (He must, so to speak, throw away the ladder after he has climbed up it.) He must transcend these propositions, and then he will see the world aright.
Tractatus, 6.54

A sticky problem indeed!

 

[ login to reply ] posted on Friday, Jul 01, 2022 06:20:34 AM
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Jorge writes:
[To Trevor Folley]

Here's something very strange. If we reject a priori and a posteriori reasoning (if I'm understanding them correctly), then the words become meaningless, and that sounds like it's true. But wouldn't it be an appeal to consequences?

I know I'm using meaning to refute meaning, but it looks like we still have a problem. 

I believe that the stolen concept fallacy is also present in P3. Why should we buy into the concept of validity of logic if logic itself is invalid? But here's another very strange thing. Using a fallacy to conclude that we should stick to logic is to use the argument from fallacy fallacy. This is because we would not simply say that the conclusion is unwarranted, but move on to say that we should accept the opposite: logic is valid.

I agree that logic is useful by the way. It's just a conundrum, or maybe a fun puzzle I guess, to wonder about these things.

[ login to reply ] posted on Friday, Jul 01, 2022 11:14:06 PM