I don't know what to call this post

Here are three things I was thinking about this morning.

* You can't prove a negative.
* Whatever can be asserted without evidence can be dismissed without evidence.
* There's no evidence for X.

You could use these to form a deductive argument.

1. There is no evidence for X.
2. (1) is a negative.
3. You can't prove a negative.
4. Therefore, you can't prove (1).
5. If (1) can't be proved, then it is an assertion without evidence.
6. Therefore, (1) is an assertion without evidence.
7. Whatever can be asserted without evidence can be dismissed without evidence.
8. Therefore, (1) can be dismissed without evidence.

That seems to shift the burden of proof, doesn't it? You'd think that if somebody were asserting X, then it would be up to that person to offer evidence for X. On the other hand, maybe it's irresponsible to say that there's no evidence for X. Maybe you should say, "I have no evidence for X," or "I'm unaware of any evidence for X," or "None of the evidence that's been presented to me so far for X has been adequate." On the face of it, (1) appears to be a claim, and if we stick by the maxim that he who makes a claim bares the burden of proof, then anybody who asserts (1) should have to offer some reason, argument, and/or evidence for it, which seems like a silly expectation. Of course I have heard people tweak the "burden of proof" principle to say, "He who makes a positive claim bares the burden of proof." If that were so, then one wouldn't need to prove (1) because it's not a positive claim. But I'm not so sure about that tweak. Negative claims are assertions, and they are often unjustified and seem to require demonstration. Suppose I said, "There are no extra terrestrial civilizations." Am I free from having to shoulder the burden of proof just because it's a negative claim and not a positive claim? It doesn't seem so.

Of course I fully expect most of my readers to reject (3), and I do, too. It might be better to say, "It's hard to prove a negative," or "Some negatives can't be proved." But negatives can be proved. I can prove that there are no flat Euclidean triangles whose interior angles add up to exactly 200 degrees. I can also prove that there's no fully grown elephant in my room. But I can't prove that there are no extra terrestrial civilizations.

I happen to also disagree with (7). I would say that in most cases, if something is asserted without evidence, you can dismiss it without evidence. It's just that there are too many counter-examples to make it a viable principle that can be asserted without qualification. Any assertion of a necessary truth is an assertion that cannot be dismissed on the basis of lack of evidence. Not only can necessary truths not be proved, but at the same time it's irrational to deny them. I can't prove the law of non-contradiction, but that doesn't mean it can just be dismissed. There are mundane claims, too, that can't simply be dismissed. Suppose your wife calls you and tells you that her car broke down, and she's stuck at Target and needs you to come pick her up, but she doesn't offer you any proof of her circumstances. Can you just dismiss her? I'm not asking whether you can dismiss her without negative consequences. I'm asking if you can rationally dismiss her. Would you be epistemologically justified in dismissing her claim merely on the basis that she didn't offer you evidence for it? I would say no. Your wife's word alone gives you sufficient justification for believing her and going out to help her. I suppose you could say the fact that she's honest and has given you her word is, itself, evidence for her claim. What, then, are we to make of the phrase, "asserted without evidence," if the assertion itself is evidence? Consider a situation where an expert is giving you facts related to their field (a history professor telling you about a battle, or a physics professor telling you about general relativity). It would seem silly to sit there, arms folded, mumbling, "Nuh uh!" the whole time. The fact that the person is an expert ought to be enough to take their word for what they're saying unless you know better for some other reason.

Isn't (7) self-refuting anyway? It is, after all, an assertion, and it's hard to think of what evidence one might provide for it. Does that mean we can just dismiss it? It seems to me that to avoid the self-refuting nature of that statement, one would have to qualify it in some way.