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An argument can be logically sound but with a false conclusion. An argument can be logically invalid but with a correct conclusion. The role of logical fallaci

by syops 6y ago

An argument can be logically sound but with a false conclusion. An argument can be logically invalid but with a correct conclusion. The role of logical fallacies is to point out unsound reasoning. They don’t demonstrate veracity or lack thereof. Regarding the appeal to authority fallacy you mentioned. I personally do not believe this is a fallacy. I do agree that the appeal to false authority is a fallacy. We all have to rely on the expertise of others for much of what we believe to be true. Of course said beliefs might be wrong but relying on expert knowledge is not a fallacy in and of itself in my opinion.

MaxBarraclough 6y ago
> An argument can be logically sound but with a false conclusion. That doesn't sound right. An argument is sound iff it is logically valid and its premises are true, right? From Wikipedia: > In deductive reasoning, a sound argument is an argument that is both valid, and all of whose premises are true (and as a consequence its conclusion is true as well) https://en.wikipedia.org/wiki/Soundness#Definition https://en.wikipedia.org/wiki/Soundness#Definition
- syops 6y ago
  I guess it comes down meaning of “sound”. Let me be more specific. An argument can correctly use the rules of logic and have an incorrect conclusion. This can happen if some of the premises are false. For example: All men are immortal. Socrates is a man. Therefore Socrates is immortal. The rules of logic have been correctly followed but the conclusion is false.
  - tpoacher 6y ago
    You mean valid. Not sound. By definition if an argument is sound, it is also valid (but not the reverse). And by definition if an argument is sound, then its conclusions are true. I think you're just mixing up the terminology a bit.
    - syops 6y ago
      Well I did use logically sound and not sound argument. I personally don’t see a difference in logically sound and logically valid but I clarified things in my previous post.
      - MaxBarraclough 6y ago
        > I personally don’t see a difference in logically sound and logically valid They aren't the same. These are standard terms in logic, as explained in the Wikipedia article.
        syops 6y ago
        Obviously I'm speaking in the vernacular and as I stated I used the terms as they meant to me. Besides logically sound and sound argument aren't the same thing in my mind. One refers to soundness of logic and the other to soundness of the argument. And that was the essence of my point. There's a difference in talking about an argument and talking about the logic used. Logical fallacies are only useful in determining if the reasoning was flawed. I didn't disagree with anything you wrote and even clarified my meaning so as to be clear. There is also the fact that, linguistically speaking, every person has a unique language. The meaning of words can vary slightly between people who nominally speak the same language. That's why I mentioned to me in my previous post. Clearly I was not writing in a mathematically precise way. I took mathematical logic in graduate school many years ago but am not qualified to use all of the terminology in a mathematically precise way. But this is an internet forum and not a course in mathematical logic. The standards of rigor are not so strict. Hence my phrase to me ought to have sufficed as far as clarification.
        mannykannot 6y ago
        "I used the terms as they meant to me... every person has a unique language." Private languages are useless for communication, which depends on shared semantics. This thread is a clear example of that, as your first post here is very misleading except to anyone who a) knows that you are using your own private language, and b) actually knows what you mean by your words. In that post, using your own private definition of the various terms under discussion is worse than useless, as anyone who does not know what the accepted meanings are will end up worse off for reading it. “When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean — neither more nor less.’ ’The question is,’ said Alice, ‘whether you can make words mean so many different things.’ ’The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.” ― Lewis Carroll, Through the Looking Glass
  - mannykannot 6y ago
    This is indeed an example of a valid but unsound argument (unsound because the first premise is false), and your use of 'sound' is correct here. Your first post, however, uses 'sound' in a manner that is inconsistent with both this example and correct usage. In particular, where you wrote "An argument can be logically sound but with a false conclusion" you presumably meant 'valid' instead of 'logically sound', as, by definition, sound arguments have true conclusions.
    - syops 6y ago
      Hence my clarification where I stated the point differently. Yes, valid would have been a better choice. Do you see that you have taken my phrase logically sound and then switched to sound arguments? Do you think these mean the same thing?
      - mannykannot 6y ago
        This is a pedantically pointless argument. In the domain of logic, 'sound' has a very definite meaning, so what are we to make of your use of the word 'sound' in a discussion of logic, especially given that you explicitly qualify it with 'logical'? What is the point of phrasing a statement in such a way that it will mislead everyone except those who can see what you actually meant? Those people already know what you are trying to say. I have not "taken [your] phrase logically sound and then switched to sound arguments". What I did, in the clause "sound arguments have true conclusions", was to make a statement of fact about the meaning of the word 'sound' in the domain of logic. On account of that being so, it would have been unequivocally wrong for you to have written "An argument can be sound but with a false conclusion." Ah, but you say (this is where it gets really pedantic) you did not write precisely that; you wrote "An argument can be logically sound but with a false conclusion" - but how do you think the modifier logically will be taken here, given that 'sound' has a specific meaning in the domain of logic? Don't tell us that (obviously!) 'logically sound' actually means 'valid'!
        xupybd 6y ago
        Communication is hard. It's harder when both parties are not using the same definitions. I've found this is one of the biggest difficulties in hashing out an argument with a stranger online. With someone I know I can spot when our definitions don't match. Online it takes a lot more back and forth and often is less friendly.
  - deleted 6y ago
    [deleted]
simonh 6y ago
I think appeal to authority gets shaky when you appeal to an authority who's domain of expertise, or specific knowledge and experience might not extend to the issue at hand. It's a matter of trusting the process of scientific inquiry, challenge and verification, not just the person. So for example I defer to Roger Penrose on anything to do with mathematics, and will absolutely he has earned a voice on astrophysics#, but quantum consciousness microtubules? Nobody is an authority on that, so who knows? # And to be clear part of his credibility there is in making it clear what he believes with a high degree of certainty and what is more speculative.
- syops 6y ago
  Yes, that is why I agree with appeal to false authority being a fallacy. This is what I was referring to in my last paragraph.
swasheck 6y ago
Those examples of appeal to authority are a lot more nuanced than I’ve generally seen. It’s generally more blunt, like “we interviewed 5 PhDs about climate change and they all state that there’s no good evidence to support it.” Those PhDs however, were not experts in a domain that could validate an assertion on climate change. The more nuanced versions in the examples make an uncritical assertion, based on an appeal to an authority in a closely related domain, to overturn an established set of “validated facts” (for the domain, say what you want about a religious creed).

by syops 6y ago

MaxBarraclough 6y ago

> An argument can be logically sound but with a false conclusion. That doesn't sound right. An argument is sound iff it is logically valid and its premises are true, right? From Wikipedia: > In deductive reasoning, a sound argument is an argument that is both valid, and all of whose premises are true (and as a consequence its conclusion is true as well) https://en.wikipedia.org/wiki/Soundness#Definition https://en.wikipedia.org/wiki/Soundness#Definition

syops 6y ago
I guess it comes down meaning of “sound”. Let me be more specific. An argument can correctly use the rules of logic and have an incorrect conclusion. This can happen if some of the premises are false. For example: All men are immortal. Socrates is a man. Therefore Socrates is immortal. The rules of logic have been correctly followed but the conclusion is false.
- tpoacher 6y ago
  You mean valid. Not sound. By definition if an argument is sound, it is also valid (but not the reverse). And by definition if an argument is sound, then its conclusions are true. I think you're just mixing up the terminology a bit.
  - syops 6y ago
    Well I did use logically sound and not sound argument. I personally don’t see a difference in logically sound and logically valid but I clarified things in my previous post.
    - MaxBarraclough 6y ago
      > I personally don’t see a difference in logically sound and logically valid They aren't the same. These are standard terms in logic, as explained in the Wikipedia article.
      - syops 6y ago
        Obviously I'm speaking in the vernacular and as I stated I used the terms as they meant to me. Besides logically sound and sound argument aren't the same thing in my mind. One refers to soundness of logic and the other to soundness of the argument. And that was the essence of my point. There's a difference in talking about an argument and talking about the logic used. Logical fallacies are only useful in determining if the reasoning was flawed. I didn't disagree with anything you wrote and even clarified my meaning so as to be clear. There is also the fact that, linguistically speaking, every person has a unique language. The meaning of words can vary slightly between people who nominally speak the same language. That's why I mentioned to me in my previous post. Clearly I was not writing in a mathematically precise way. I took mathematical logic in graduate school many years ago but am not qualified to use all of the terminology in a mathematically precise way. But this is an internet forum and not a course in mathematical logic. The standards of rigor are not so strict. Hence my phrase to me ought to have sufficed as far as clarification.
        mannykannot 6y ago
        "I used the terms as they meant to me... every person has a unique language." Private languages are useless for communication, which depends on shared semantics. This thread is a clear example of that, as your first post here is very misleading except to anyone who a) knows that you are using your own private language, and b) actually knows what you mean by your words. In that post, using your own private definition of the various terms under discussion is worse than useless, as anyone who does not know what the accepted meanings are will end up worse off for reading it. “When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean — neither more nor less.’ ’The question is,’ said Alice, ‘whether you can make words mean so many different things.’ ’The question is,’ said Humpty Dumpty, ‘which is to be master — that’s all.” ― Lewis Carroll, Through the Looking Glass
- mannykannot 6y ago
  This is indeed an example of a valid but unsound argument (unsound because the first premise is false), and your use of 'sound' is correct here. Your first post, however, uses 'sound' in a manner that is inconsistent with both this example and correct usage. In particular, where you wrote "An argument can be logically sound but with a false conclusion" you presumably meant 'valid' instead of 'logically sound', as, by definition, sound arguments have true conclusions.
  - syops 6y ago
    Hence my clarification where I stated the point differently. Yes, valid would have been a better choice. Do you see that you have taken my phrase logically sound and then switched to sound arguments? Do you think these mean the same thing?
    - mannykannot 6y ago
      This is a pedantically pointless argument. In the domain of logic, 'sound' has a very definite meaning, so what are we to make of your use of the word 'sound' in a discussion of logic, especially given that you explicitly qualify it with 'logical'? What is the point of phrasing a statement in such a way that it will mislead everyone except those who can see what you actually meant? Those people already know what you are trying to say. I have not "taken [your] phrase logically sound and then switched to sound arguments". What I did, in the clause "sound arguments have true conclusions", was to make a statement of fact about the meaning of the word 'sound' in the domain of logic. On account of that being so, it would have been unequivocally wrong for you to have written "An argument can be sound but with a false conclusion." Ah, but you say (this is where it gets really pedantic) you did not write precisely that; you wrote "An argument can be logically sound but with a false conclusion" - but how do you think the modifier logically will be taken here, given that 'sound' has a specific meaning in the domain of logic? Don't tell us that (obviously!) 'logically sound' actually means 'valid'!
      - xupybd 6y ago
        Communication is hard. It's harder when both parties are not using the same definitions. I've found this is one of the biggest difficulties in hashing out an argument with a stranger online. With someone I know I can spot when our definitions don't match. Online it takes a lot more back and forth and often is less friendly.
- deleted 6y ago
  [deleted]

simonh 6y ago

I think appeal to authority gets shaky when you appeal to an authority who's domain of expertise, or specific knowledge and experience might not extend to the issue at hand. It's a matter of trusting the process of scientific inquiry, challenge and verification, not just the person. So for example I defer to Roger Penrose on anything to do with mathematics, and will absolutely he has earned a voice on astrophysics#, but quantum consciousness microtubules? Nobody is an authority on that, so who knows? # And to be clear part of his credibility there is in making it clear what he believes with a high degree of certainty and what is more speculative.

syops 6y ago
Yes, that is why I agree with appeal to false authority being a fallacy. This is what I was referring to in my last paragraph.

swasheck 6y ago

Those examples of appeal to authority are a lot more nuanced than I’ve generally seen. It’s generally more blunt, like “we interviewed 5 PhDs about climate change and they all state that there’s no good evidence to support it.” Those PhDs however, were not experts in a domain that could validate an assertion on climate change. The more nuanced versions in the examples make an uncritical assertion, based on an appeal to an authority in a closely related domain, to overturn an established set of “validated facts” (for the domain, say what you want about a religious creed).