Argument from ignorance: What?

[Speakpigeon]

Can we disprove Joe's claim that he knows that p by arguing that Joe ignores whether some specific situation falsifying p isn't the case.

For example, Joe may claim to know the Donald Trump is the president of the United States of America. Is it then possible to falsify Joe's claim to knowledge by arguing that Joe doesn't know that the real Donald Trump died age 2 and that the guy posing as Donald Trump is, guess what, the older brother of Vladimir Putin!

Yes, and this his is a very simple logical point.

I know that p implies that p is true. This is fundamental to knowledge.

And if p is true, then there is no possibility that p is false. Thus, if I know that p, then there is no possibility that p be false. However, if you don't know that there is no possibility that p be false, then you cannot exclude that p is false, and therefore it is possible, for all you know, that p be false, which falsifies your claim to know that p is true.

Please note the distinction between not knowing that there is no possibility that p is false and p actually being false, just as there is a distinction between ignoring that p is false and p actually being false.

Thus, an argument from ignorance can only at best falsify a claim to knowledge, not whether what is claimed to be true is in fact false.

We all claim to know things all the time and very often when we don't in fact know what we are talking about. For example, some Joe may claim to know that monkeys don't fly. Suppose now that the next day a new species of monkeys is discovered and that these monkeys do fly! This would falsify the claim that monkeys don't fly and therefore Joe's claim that he knew that monkeys don't fly.

However, the most important point is that although Joe's claim is falsified only the next day, his claim was in fact already false the moment he made it. Thus, Joe didn't know, and never knew, what he had claimed to know that monkey didn't fly.

Usually, we genuinely believe we know what we claim to know. Yet, experience shows again and again that we can be wrong, and it is the simple possibility of being wrong, even if it is that we might be wrong, which falsifies our claims to knowledge.

I know that p implies that p is true. If I know p, then p is true. And if p is true, then there is no possibility that p is false. But if I don't know that there is no possibility that p is false, I don't know that p is true, which falsifies my claim to knowledge.

That in itself won't stop people claiming they know. This is entirely a practical matter.

In effect, whatever we believe we know to be true may in fact be false and there isn't much we can do about that. Most of the time, however, if you are somewhat conservative and prudent and reasonable in whatever claims you make, you won't be contradicted by the facts of the matter.

It is a fact of life that we will claim that p whenever we happen to believe with a high enough degree of confidence that p is true.

Thus, even though most of the time we don't know that p, we will nonetheless claim that p just because we believe that p, and because from experience we believe that most of the time, we won't be contradicted by the facts of the matter.

In practice, it is worth claiming you know all sorts of things again and again, even if it is not true that you know them, because if you are reasonable in your claims, experience shows that you won't be contradicted so often as to damage your standing in society. In other words, we don't feel like we need to fuss too much about our claims to knowledge.

This only apply to everyday life but it is everyday life that drives the way we use basic words like "know" and "believe". Hence, we will use the word "know" even when in fact we only believe, and this merely because we also believe we will get away with it, at least most of the time.

There is another aspect to the question, though, somewhat more subtle, but your question is right on spot.

An argument from ignorance should identify a possibility and not everything will do in that respect. For example, if you say, well, you don't know that p because you don't know that it is not possible that q and not q. This wouldn't work because in fact we do know that it is not possible that q and not q.

There is another case of ineffective argument from ignorance and this is when the situation that you are supposed to ignore whether it is possible or not just doesn't make sense. It is my opinion that the notion that we are in a simulation is nonsensical.

However, irrespective of whether my opinion on this is correct or not, the fact remains that nonsensical situations are ineffective for an argument from ignorance. We need to understand what it is we are supposed to not know that this isn't the case. The reason for that is simple. If we don't understand what is the situation involved in the argument, then we won't be able to decide whether we actually don't know that it is not the case.
EB

 

[Bronzeage]

So basically, you can have your facts straight and still be wrong.

 

[fromderinside]

Nice. Not many words.

Still utterances (spoken, drawn, or text) are never based on actual events and phenomena. Rather they are second hand gatherings from sense and memory of energy generated by actual events and phenomena. And there are instruments that read these tea leaves in direct physical terms at the appropriate scale that are always better than to what a human has access otherwise.

As far as 'knowing' we can say we know because we define what is 'knowing'. However what is known is never what one knows rather it is gathered from that approximation package I presented above, so at best, an approximation.