How do we prove that the laws of logic are metaphysical

[VanVos]

How do we respond to an atheist who says that the laws of logic are a product of the human mind/brain, and that all human minds function in the same way, and therefore logic is binding as long as there are human minds/brains . How do we prove that the laws of logic are metaphysical and exist outside of own existence.

I have argued that if the laws of logic only exist within the human mind then they couldn't be universally binding on all human minds. In others words if there claim was true then we would have multiple laws of logic, making them subjective rather than objective. Is this sound argumentation?

VanVos

[Edited on 10-23-2005 by VanVos]

 

[Saiph]

Nature itself abides by the law of logic. A/~A

 

[VanVos]

True. But don't be shy. Feel free to expound.

 

[Saiph]

First of all, does this person understand that the mind is not the physical organ called the brain ? Mind and brain may be existentially inseparable, and so regarded as one and the same thing, yet the mental and the physical are analytically distinct aspects of it.

It is not laws of logic being subjective that is the problem. It is probably their denial of the imago dei that stands apart and against nature, in that we uniquely observe and utilize these laws of logic in thought and action. It is their naturalistic material idea of what we call "soul". The brain is not the sufficient condition for intellectual activity and conceptual thought in the human mind, which is not the case for animals. This immaterial factor is created by God, after His image, and yet bound to the law of the flesh as Paul says, until it be regenerated. They supresses this truth because their thoughts are antithetical to God's character.

But, I lean more Thomist than Van-Tillian, so maybe I am deceived.

[Edited on 10-23-2005 by Saiph]

 

[Saiph]

So in other words, when you asked:

How do we respond to an atheist who says that the laws of logic are a product of the human mind/brain, and that all human minds function in the same way, and therefore logic is binding as long as there are human minds/brains . How do we prove that the laws of logic are metaphysical and exist outside of own existence.

Get them to realize that the mind/brain are seperate things. Man is not merely a physical biochemical machine. And praying for their conversion seems to help sometimes too.

 

[VanVos]

Get them to realize that the mind/brain are seperate things. Man is not merely a physical biochemical machine. And praying for their conversion seems to help sometimes too.

btw this person is hypothetical

Okay. But how does one prove that i.e. that the laws of logic are metaphysical. Plus I believe man is a substantival monism.

VanVos

 

[Saiph]

By substantival monism, do you mean that the brain and mind are the same thing ? So at death where does the mind, will, and emotions(soul) end up ?

If that is true, then the laws of logic are no more than the chemical result of what you eat.

Actually Johnathan, I have a hard time with the idea of proof or proving anything to an unregenerate person. Faith provides proof.

I am not a fideist. And the trancendental argument of Van Til does prove God's existence in one sense. But the fall effects the noetic process of the unregenerate as well.

Maybe I cannot answer your question.

[Edited on 10-23-2005 by Saiph]

 

[VanVos]

By substantival monism, do you mean that the brain and mind are the same thing ? So at death where does the mind, will, and emotions(soul) end up ?

If that is true, then the laws of logic are no more than the chemical result of what you eat.

I'm refering to Greg Bahnsen material on this issue http://www.cmfnow.com/articles/pa143.htm

Actually Johnathan, I have a hard time with the idea of proof or proving anything to an unregenerate person. Faith provides proof.

I am not a fideist. And the trancendental argument of Van Til does prove God's existence in one sense. But the fall effects the noetic process of the unregenerate as well.

Maybe I cannot answer your question.

I see what your saying, for example Heb 11:6.

VanVos

Btw I appreciate your comments, thanks

 

[August]

I'm not sure I understand the question. The laws of logic are by definition metaphysical, i.e. part of the theory of knowledge and being. As for proving absolute immaterial laws of logic, we first have to explore the atheist statement further, if we are to understand what logic he is going to use to understand us. If the laws of logic work as he states, as a product of the human mind, and that all human minds work in the same way, he has to prove that, without using the laws of logic so as not to be circular. Does it mean that the minds of a 3 year-old Ethopian, a 90 year old Alzheimers sufferer and his all work in the same way? Remember, his statement is an absolute, and he has to prove it without using what he is trying to prove.

[Edited on 10-24-2005 by August]

 

[Saiph]

(if thoughts are even "inside" brains, which they are not).

Amen.

 

[Saiph]

Found this today Johnathan. Thought it was relevant to the discussion of logic. Since logic is immutable.

Augustine´s favourite theistic proof was via consideration of the process of thought. He said that truth is immutable. To think immutable truths with our mutable minds means "our mind is so to speak in contact with something that is immutable and eternal" which is God, the ground of all truth.

W Brueggemann, (1997), Theology of the Old Testament


Still trying to find the actual reference in Augustine's works.

 

[JohnV]

This is a trap. Once this argument is given, then anything you may say, whatever response you give, it can never be anything more than your opinion or your presupposition. Even if you state your case cogently, all it will ever be is interesting to listen to, at best. That's the idea behind it. For all intents and purposes, any appeal to truth has been cut off.

What he thinks he has is an unassailable position. His problem should be that it is also a useless position, because he has also cut himself off from saying anything useful; i.e., truth is not relevant to his position either.

All you need to do is neither take the offensive nor the defensive. Rather try to make him take the defensive after he has made this assertion. Paul M. makes a very good set of questions to do that with. In other words, he must fall into his own trap; but you must remain aloof from it. If he is at all interested in seeking real truth, he will know the weakness of his position.

But usually such assertions are boastful attacks which work on the defensive positions people usually take automatically. If you can remember that truth is not your truth, but God's, and that God is attacked, and then that this person feels he has a reason to attack God, then you will much sooner see his need and minister to it. If you're out just to win arguments, well that's what this trap is meant for, to catch those kinds of people. Just don't fall for it.

 

[Saiph]

JohnV,

You lost me brother. Are you saying the idea of logic being immutable is a trap ?

How does logic change ?
How can anyone live or even reason consistently without logic ?

 

[JohnV]

Mark:

No, I mean the idea that laws of truth or truth itself is only as sure as man's mind is. It works this way: Mr. A states that he believes that the laws of logic exist only as a product of human intellect. The expected response is a defensive position taken on the laws of logic. Any argument you would give to counter this assertion would be, to him, a product of the human intellect, and therefore a mere use of the laws of logic to the extent preferred by that intellect. In other words, the intellect of one has no authority on the intellect of another. So the laws of logic have no authority.

 

[JohnV]

Sorry, I didn't meant to be cryptic. I'm having problems keeping control of this new computer with a touch pad.

Of course the laws of logic are authoritative. Mr. A would not be able to say what he is saying if they weren't. But he's trying to catch someone in the trap of defending his own presuppositions as if they were authoritative, and he's doing that by surreptitiously equating the two. It's a subtle trap.

 

[knight4christ8]

If you really want to dig in, read Thomas Nagel's book THE LAST WORD.

The atheist cannot justify his judgment that the laws of thought are a human convention without relying on the universiality of the laws of thought in order to make such an objective judgment.

 

[VanVos]

Thanks for your comments everyone, very helpful

 

[Civbert]

Originally posted by VanVos
How do we respond to an atheist who says that the laws of logic are a product of the human mind/brain, and that all human minds function in the same way, and therefore logic is binding as long as there are human minds/brains . How do we prove that the laws of logic are metaphysical and exist outside of own existence
...
VanVos

[Edited on 10-23-2005 by VanVos]

You don't prove them. You can't prove them. This is one case where contrary is impossible - but even this argument is circular since it presupposes logic.

It does not matter if they do not exist outside the human mind, but Van Til might approve.

I think others have answered better then I that you can ask him to prove that outside the human mind they do not exist - I think it will be easier to prove the atheist does not know he himself exits.

The question is like asking can God make a rock so big he can not lift it - only the metaphysical question is more pointless.

 

[VanVos]

Originally posted by CivbertYou don't prove them. You can't prove them. This is one case where contrary is impossible - but even this argument is circular since it presupposes logic.

Actually I would somewhat agree. We can prove it by the impossibility of the contrary. But such proof is legitimate because it's a transcendental argument.

Originally posted by Civbert It does not matter if they do not exist outside the human mind, but Van Til might approve.

You mean Vantil might disaprove, right?

Originally posted by CivbertI think others have answered better then I that you can ask him to prove that outside the human mind they do not exist - I think it will be easier to prove the atheist does not know he himself exits.

Interesting approach, but I think I still prefer the TAG.

Originally posted by CivbertThe question is like asking can God make a rock so big he can not lift it - only the metaphysical question is more pointless.

I'm sorry, I you saying the apologist shouldn't attempt to prove the laws of logic?

VanVos



[Edited on 12-3-2005 by VanVos]

 

[mgeoffriau]

Actually, while the points made are good, I'm not sure the discussion has to go even that far.

I would point out to this hypothetical person that by denying the universality of the laws of logic, he has also denied himself the ability to make that statement meaningful.

Without universal, necessary laws of logic, he can no longer make any meaningful statements, and cannot communicate.

The very fact that he has attempted to communicate and has assumed that you will be able to hear, understand, and respond to his statement reveals that he implicity is forced to believe in the universality of the laws of logic.

When he says, "The laws of logic are the product of man's mind," you can say, "If that is true, then you cannot know that that is true."

Others have said this, I just wanted to restate in a format that seemed simpler and more direct.

 

[VanVos]

I do agree. That's how you could approach it when having dialogue with such a person. But to put it more epistemologically: You prove the laws of logic by reasoning transcendentally, i.e. the impossibility of the contrary.

VanVos

 

[Civbert]

Originally posted by VanVos
I do agree. That's how you could approach it when having dialogue with such a person. But to put it more epistemologically: You prove the laws of logic by reasoning transcendentally, i.e. the impossibility of the contrary.

VanVos

What are the implications of the laws of logic existing internal or external to the mind of man?

Either way, the laws of logic are self-evident. And if we argue for the impossibility of the contrary (which is a good argument for showing the futility of denying logic) it does not answer the question.

 

[VanVos]

In order for the laws of logic (as a conceptual scheme) to be objective and binding upon all men they must be external . To make them only internal is to open the door to subjectivity.

I believe it does answer the question, because then the laws of logic are proven to be a neccessary precondition for the intelligability of man's experience. But I'm come from a Vantillian perspective here.

 

[Civbert]

OK. I understand. I was thinking of the laws of logic as common and the same to the minds of men, regardless if they are also external to the mind. If you think about it, if logic is only a function of human minds - that says nothing about if they are the same laws for all human minds or not. But to the atheist, it makes no sense to consider logic "external" to the mind because logic is rational thinking - and the without a mind - logic has no function. But logic may be univocal to all rational minds non-the-less. In a way, Van Til seemed to say that logic was applicable the the created mind - for it functioned on the level of creation.

As for the necessity of logic for intelligibility - that is a Clarkian sentiment as well. The difference between Clark and Van Til was that Clark did not say the presumption of the Christian God was a necessary precondition of logic - were Van Til said it was.

Clark said logic was self-evident for all people - regenerate or not. Van Til believed that logic is not possible without assuming a Christian world-view. But this is an assertion Van Til could never prove from a priori knowledge.

[Edited on 12-3-2005 by Civbert]

 

[JohnV]

I once was a member of a Round Table, set up like E Stanley Jones' model. There was a new ager there. One time we were discussing contradictions as indicators of falsehoods, and he kept interjecting that contradictions were a part of reality, and therefore part of God as well.

I was the only Five-point Calvinist there, and I kept pointing out that the Law of Contradiction was akin to the opposites of Faithfulness and Unfaithfulness. Well, he had had it with me especially, and blurted out that contraditions led us nowhere, since God Himself had contradictions. I knew I was not going to get anywhere with him, because even the simplest examples didn't phase on him. So eventually we said to him, "I know; that's why I wasn't afraid to say it." to each objection of his.

At first it didn't hit him what we had done. But everytime he cut in again with his objection we replied in the same way. Then it hit him, and he kept quiet after that. He finally understood that to hold to the Law of Contradiction was just as legitimate as anything he wanted to offer, because his view did not have any ground against it; and at the same time it was just as legitimate in anything we said. We turned his argument against him, where it belonged. We just stole his thunder, you might say.

 

[VanVos]

Originally posted by Civbert
OK. I understand. I was thinking of the laws of logic as common and the same to the minds of men, regardless if they are also external to the mind. If you think about it, if logic is only a function of human minds - that says nothing about if they are the same laws for all human minds or not. But to the atheist, it makes no sense to consider logic "external" to the mind because logic is rational thinking - and the without a mind - logic has no function. But logic may be univocal to all rational minds non-the-less. In a way, Van Til seemed to say that logic was applicable the the created mind - for it functioned on the level of creation.

Yes logic is rational thinking. But the *laws* of logic to be laws have to exist independently of human minds.

Originally posted by Civbert
As for the necessity of logic for intelligibility - that is a Clarkian sentiment as well. The difference between Clark and Van Til was that Clark did not say the presumption of the Christian God was a necessary precondition of logic - were Van Til said it was.

Clark said logic was self-evident for all people - regenerate or not. Van Til believed that logic is not possible without assuming a Christian world-view. But this is an assertion Van Til could never prove from a priori knowledge.

[Edited on 12-3-2005 by Civbert]

In my understanding Vantil was a transcendental presuppositionalist, where Clark was dogmatic presuppostionalist. Vantil said that the Triune God was the necessary precondition for the intelligibility of man's experience. The laws of Logic are conceptual therefore it needs to proceed from a divine mind. We also need to be able to unify particulars therefore we need a Triune God. The Christian worldview is the only worldview that can *account* for this. And since it's a transcendental argument it's the *only* true worldview.


[Edited on 12-4-2005 by VanVos]

 

[Nomos]

Paul Manata said:

"As a side, even the self-evidency of logic has been questioned. For example, look at the critiques of, say, the law of excluded middle."

I don't think the plethora of paradigms of logic (institutional logics, modal, doxastic, deontological, dialectical and paraconsistent logics) undermines the self-evidential nature of the necessity of some sort of normative means of evaluating human cognition. After all, one cannot effectively argue for one paradigm of logic itself without first assuming some sort of normative idea as to how to evaluate these things. Therefore, to question one 's evaluative framework is to assume another. As they say, there is no neutrality.

Rev Jonathan James Goundry said:

"How do we respond to an atheist who says that the laws of logic are a product of the human mind/brain?"

I would respond by inquiring into what is meant by 'product of the human brain'? If they mean some sort of chemical/neurological output of the cognitive apparatus, then I would question as to the nature of that output. How does one associate neurological functioning with abstract categories like principles/laws of thought? How does one evaluate varying kinds of neurological/cognitive functioning and how would one even begin to account for that standard of evaluation?

In other words, simply labeling the way we think as a 'product' of our brain is hardly sufficient in itself to 1] provide a means to evaluate that very proposition, and 2] provide a means to evaluate one cognitive product from any other.

Debate is stultified for someone that takes this view.

 

[Magma2]

How do we respond to an atheist who says that the laws of logic are a product of the human mind/brain, and that all human minds function in the same way, and therefore logic is binding as long as there are human minds/brains . How do we prove that the laws of logic are metaphysical and exist outside of own existence.

I have argued that if the laws of logic only exist within the human mind then they couldn't be universally binding on all human minds. In others words if there claim was true then we would have multiple laws of logic, making them subjective rather than objective. Is this sound argumentation?

Just my two cents. I think you´re is on the right track since the atheist wants to use logic to justify himself yet he cannot account for it. Frankly, I think the downfall of all non-Christian philosophy is its failure to account for logic. On the positive side, I would recommend Gordon Clark´s article, God and Logic, for a brief overview of what I think is the biblical response. In addition, on another thread I posted the following argument for LC and LEM by George Coghill which may provide some assistance in providing an account to the atheist´s inevitable non-answer.

That lc and lem are deliverances of scripture comes from 1 John 2:21:

No falsehood (pseudos) is of the truth.

That as it stands is a pretty good declaration of the law of contradiction. It says that there is no proposition (x) that is both a falsehood and of the truth (ie a member of the class of true propositions).

Note that this is a universal negative. That is, it applies to every member of the class, which in this case is propositions. Now, that it applies to all propositions not just those in scripture should be obvious from the fact that there are no falsehoods in scripture.

Let Tx stand for 'x is of the truth', and Fx stand for x is a falsehood.

Then we can put it into symbolic logic as:

~3x(Fx & Tx) ---(1)

where '~' means 'not' and '3x' means 'there exists an x'

By de Morgans laws this is equivalent to:

~3x~(~Fx + ~Tx) ---(2)

Now in scripture there are (as far as I can see) only two types of proposition spoken of: true ones and false ones. (If you disagree then please show where scripture indicates differently.) Also as far as I can see these two are in contradiction to one another (see the references Sean gave the other day). Again if you disagree then please show the error from scripture. If this is the case

That being the case (2) can be rewritten as:

~3x~(Tx + Fx)

Then by quantifier conversion this becomes:

(x)(Tx + Fx)

(where '(x)' means 'for all x')

Restating this in longhand it becomes:

For every proposition, x, it is the case that either x is of the truth or x is a falsehood.

And that is the law of the excluded middle.

[I used predicate logic first because it is easier to see what is going on and since when talking about contradictions predicate logic andaristotilian logic give the same results.]

For completeness, I shall do the same with Aristotilian logic:

No falsehood is of the truth can be written formally as:

E(F,T)

which by conversion can also be written as:

E(T,F)

As I said that is as good a statement as any of lc.

Then by obversion this becomes:

A(T,F')

and since T is equivalent to F' (as stated previously) we get

A(T, T) ---(3)

which is the law of identity.

Now recall from Clark's "Logic" that the universal affirmative can be written in symbolic terms as:

A(a, b) = (a < b)[(b < a) + (a < b')'(b' < a)']

So substituting from (3) into this gives:

(T < T)[(T < T) + (T < T')'(T' < T)]

Expanding gives:

(T < T)(T < T) + (T < T)(T < T')'(T' < T)

I am not going to go through this step by step (you can check it for yourself) but it should be pretty obvious that the left hand side of this disjunction reduces to 'T" and the right hand side reduces to 'F'

So we have:

T + F

Which is the law of the excluded middle, and states that every proposition is either of the truth or is a falsehood.

As a final note. This should be taken as a demonstration that lc and lem are deliverances of scripture. Since one has to assume them in order to proceed it constitutes proof only in the sense of implicit self reference along the lines of 2 Tim 3:16 or God swearing by himself.