Nothing. Nothing at all.
Well, that’s the quick answer. But now some more detail.
Commenting on my previous post, Philomath asked:
If everyone agrees on something do that make it true?
He clearly saw this question as relevant to my posts on knowledge. My title question arises from this. My own view of knowledge is such that there are no truth criteria for having knowledge.
There’s an old saying:
- if the only tool you have is a hammer, then every problem looks like a nail.
The version of this for philosophy is:
- if the only tool you have is logic, then every problem looks like a proposition.
Philosophers — or, at least, analytic philosophers, attempt to discuss everything in terms of propositions and the truth values for those propositions. I see that as a mistake.
Let’s suppose, for the moment, that Philomath is a theist. Then we might plausibly assume that he/she has a lot of knowledge of theology. But, at some future time Philomath might decide that it is all false, and become an atheist. Yet he/she would still have that same knowledge of theology. That he/she sees it as not true has no bearing on whether it is knowledge. It might make that knowledge less useful and less important. But it does not make it not knowledge.
So, at least in ordinary usage, truth does not seem to matter as to what counts as knowledge.
Suppose you ask whether I believe it is raining. I will probably look out the window to see. Here “It is raining” is a proposition. Looking out the window will provide me with evidence that I might claim justifies believing that proposition.
But if I know that it is raining, I won’t look out the window. I won’t need evidence, because my knowledge already justifies the belief. Perhaps I have been hearing the sound of the constant patter of raindrops on the roof or against the windows. Or perhaps I was just outside. It doesn’t much matter. I don’t need evidence, because I am already familiar with the fact that it is raining.
I’m suggesting that “knowledge” or “knowing” refer to my familiarity rather than to a particular propositional form or its truth. I’m tentatively inclined to say that all knowledge is acquaintance knowledge (familiarity) or procedural knowledge (acquired skills) or some combination of both.