I have read the the criteria to determine if an argument is sound is if its claim is valid and its premises are true.

However, what if no one can know whether or not an argument is sound because no one can evaluate its claim as valid and its premises are true?

For instance, take the following argument:

  1. Socrates is a man.
  2. All men are mortal.

Therefore, Socrates is mortal.

Would such inability to evaluate that the claim is valid and its premises as true imply that the argument is not sound, or would such imply that such argument should not be claimed as sound because its parts cannot be verified.

If the latter, why is it that if an argument cannot be known as sound it could still be considered sound?

Is a pre-requisite for an argument to be claimed as sound that it can be known as sound? If not, why not?


Would I be right to presume there is a difference between (1) claiming an argument is sound and (2) whether or not an argument is sound?

Update 2:

It appears to me that in order to claim an argument as sound, a claimant must know that the argument's claim be valid and its premises true rather than the argument's claim be valid and its premises true in order to prevent a false or speculative claim of soundness.

Still, it seems to me if no one can know an argument is sound, then it cannot be sound because for at least one person to be able to know an argument as sound implies that the argument's claim can be known as valid and its premises as true, which implies that that the argument is sound.

  • If we allowed arguments for which we cannot decide the premises as true or false, to be sound, then we could have arguments where all premises turn out to be eventually false, but for which we had already granted the conclusion as true. That doesn't seem prudent.
    – Frank
    Mar 26, 2023 at 21:47
  • Are you implying that claiming an argument to be sound requires that its claim can be known as valid and its premises known as true? Mar 26, 2023 at 21:51
  • Yes. If you can't establish the truth of falsity of the premises, the argument is worthless.
    – Frank
    Mar 26, 2023 at 22:04
  • 1
    This is intro-philosophy stuff. > A valid argument need not have true premises or a true conclusion. On the other hand, a sound argument DOES need to have true premises and a true conclusion: Soundness: An argument is sound if it meets these two criteria: (1) It is valid. (2) Its premises are true.
    – Boba Fit
    Mar 26, 2023 at 22:31
  • 1
    For formal arguments it is easy to tell whether they are valid, they just have to follow a set of deduction rules that even a computer can check. There are no rules to tell if the premises are true. If they are the argument will be sound even if that is unknown, but to claim that they are one would need evidence in support of that claim acceptable to the opposition, i.e. more arguments until uncontested premises are reached.
    – Conifold
    Mar 27, 2023 at 6:31

2 Answers 2


The purpose of arguments is, roughly speaking, to convince people of things. More specifically, the purpose of an argument is to convince someone of the conclusion, based on premises that they accept as true (or could be convinced to accept as true).

For this, the speaker and the listener both need to agree that the argument is sound.

The question is not so much whether the argument is actually sound, because we don't have access to objective truth (but we can get closer to objective truth using tools like science and logic), so we can't be completely sure whether an argument is actually sound. But rather, the question is whether we are justified in believing the argument to be sound. This is a subtle, but important, distinction.

The speaker can make whatever baseless claims they want about the soundness of the argument, but this would be largely irrelevant. The more important consideration is the justification they give for claiming it to be sound, and the question is whether the listener accepts the soundness of the argument.

For one to accept that an argument is sound, there should be sufficient justification to believe that the premises are true.

If it is not known whether a premise is true, then the argument should not be accepted as sound and the conclusion should not be accepted on the basis of the argument (this also doesn't mean that the conclusion should be rejected, as one may or may not have other reasons for accepting the conclusion).

  • +1 "It does not matter whether the argument is actually sound." Exactly, and a central contention of On Bullshit.
    – J D
    Mar 28, 2023 at 16:56
  • If it doesn't matter if an argument is sound, it can simply be dismissed as unsound and that would the end of it. We do care if an argument is really sound. At least for a discussion to take place.
    – Nikos M.
    Mar 28, 2023 at 18:29
  • 1
    @NikosM. I rephrased that part a bit.
    – NotThatGuy
    Mar 29, 2023 at 8:51

However, what if no one can know whether or not an argument is sound because no one can evaluate its claim as valid and its premises are true?... why is it that if an argument cannot be known as sound it could still be considered sound?

So, central to your question is the notion of knowledge. All the rest circulates about the notion of knowing, and before any philosopher would wade into explicating on this matter, it would behoove said philosopher to address what the meaning of known is. It also might help to drag out the difference between appearance and actuality.

So, the problem of radical skepticism essentially argues that knowledge isn't possible, and for a radical skeptic, then sure, no argument has any sort of privileged role in sorting out what is actually known from what is merely believed. Problem solved. Words are mostly useless, all claims are equal. There is no actuality, but only appearance. Except this is an absurd position reserved for Greek and Roman skeptics and teenagers on a crash course for existential crisis.

What modern philosophy of logic has to offer is the notion of defeasible reasoning (SEP), which is the idea that claims can be treated as truths until defeaters come along and force the thinker to reevaluate what is and isn't true. Now, in the olden days, philosophers craved certainty and wanted truth to be objective, like reality itself. If a tree is a public experience, than truth should be too. The problem is unlike a tree, which is subject to the rigorous of scientific methods and empiricism, truth is a concept and is at best an abstract object (SEP). Truth doesn't grow on trees.

So how is truth and knowledge to be had? It seems to boil down to the notion of justification or judgement which itself is a bit murky. What does it mean to justify a belief? Dismissing Gettier's objection as academic, the general notion that we undertake some specific process to ensure that belief is true and thus a belief can be claimed as knowledge is highly domain specific. Stephen Toulmin in his Uses of Argument provides us a very tidy semantics for discussing informal argumentation. Justification can be seen as vetting belief through argumentation by providing backed warrants and examining rebuttals and exploring a topic until we sift the wheat from the chaff. In fact, in informal argument, unlike it's more formal relative, we don't even use the terms valid and sound, but instead talk of strength and cogency giving the words themselves a more probabilistic flavor. And that's the point to be made.

If you are apprising how logical an argument is, you are trying to prove truths are objective, you are just trying to shoving them past reasonable doubt, a phrase you might here uttered in the more real-world context of law. That's because justification or judgement in real world thinking, not the stuff of obnoxious pedantry, relies heavily on philosophical intuition (SEP), and why many people believe an argument when even the argument made is obviously philosophical bullshit. There are pervasive fallacies and cognitive biases, deception, confabulation, and hallucinations to contend with, and to be sure that something is true without the possible of future revision of belief is a bad idea in the real world. In fact, this notion that human belief is fallible is central to the doctrine of fallibilism.

What's important to know is that argumentation as persuasion relies on non-rational factors including intuition, emotional appeal, and even the character of the person making the argument, the familiar ethos, pathos, and logos we know and love. And even when it comes to the language-games surrounding logos, certainty is hampered by honest error and deliberate action. The idea that you can appeal to aprioriticity for certainty in the Euclidean axiomatic method is an important facet of reasoning, but it's neither typical nor exhaustive of reason in everyday life. Most people rely on surface clues and shallow justification to arrive at truth, largely on an economics of attention. And that is why many people see soundness where further inspection reveals doubt. Arguments are just words that guide us to other words mired in still other words and our feelings and experiences.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .