I have an interstellar spacecraft in my basement. Come take a look!

Let’s talk about testimony some more in dialogue with Silver Bullet. In a recent comment SB quotes little ole’ me as I observe:

“So it is testimony that wears the trousers (to be politically incorrect) and it is through testimony that we can gain all sorts of properly basic beliefs ... Absent defeaters we are justified in holding those beliefs ... Note the "absent defeaters" bit. There can be defeaters that undermine a particular individual as being a trustworthy or reliable source of information."

SB then launches off at this point:

“Ok, well suppose that someone trustworthy and reliable as a source of information tells you the following:

a) "I have a car"
b) "I have a nuclear weapon"
c) "I have an interstellar spacecraft"

“Have you just gained 3 properly basic beliefs? No evidence required for any of these 3 claims?”

Zoiks! Is this really a question? Okay, I have restrained the snide little devil on my left shoulder and will let my response be governed by the angel on my right. In other words, I will deal with the question straight even though I think SB really knows how to answer it. (At least I hope SB does.)

I have a car

Let’s start with “I have a car.” If “someone trustworthy and reliable” told you they had a car would you believe them? All things being equal I certainly would. I’d also believe them if they said the weather forecast for tomorrow said below average temperatures. This ain’t rocket science ... yet.

I have a nuclear weapon

Now what if the person said “I have a nuclear weapon”? Would I believe the person without evidence in that case? It depends. First note the ambiguity of “have”. It could mean “have in my possession” or it could mean “have access to”. There are some people who might have access to a nuclear weapon. I would doubt the young man who delivers the newspaper if he made either claim, but I would probably believe my buddy who works at the Los Alamos National Laboratory if he claimed to have access to such weaponry.

I have an interstellar spacecraft

I wouldn’t believe this because there is an excellent defeater to the claim. NASA and the European Space Agency have not yet developed viable inter-planetary spacecraft and thus are very far away from interstellar spacecraft. But if NASA and the European Space Agency don’t have such craft then it is highly unlikely that my friend does, even if he works at the Los Alamos National Laboratory. So yes that would be a defeater for the claim.

Final question: what if my friend said: “I have the craft in my basement. Come take a look!” Would I go? Maybe. But if I noticed that he had a strange glazed expression and was holding a bloodied wrench, I’d probably let him walk down the stairs first.

Summing Up

So we could rationally believe (a) and if it is true then we could know it. It is possible but very unlikely that we could rationally believe (or know) (b). And it seems to me impossible that we could rationally believe (c) apart from the provision of very strong evidence to show that the individual has something that is possessed by neither NASA nor the European Space Agency.