Kenny wrote:
How about this one; Prove Santa Clause does not exist! To do this you would have to comb every inch of the North Pole, while checking all the air space over the world just in case he is cruising around in that flying sleigh he is known to ride around in.
Exactly.
I was waiting for this old chest nut. I have good reasons to believe he doesn't exist, actually very strong ones. (unless you mean his clones that walk around at Christmas
)
We could go through them if you like, but I think you know what they are.
Kenny wrote:
It is easy to think of a scenario when a negative can be proven, but often negatives cannot be proven. A friend of mine recently claimed he could still dunk a basketball like he did when he was in high School. (he is over 40 years old) I doubted and he dunked proving his claim correct. Now suppose he were to ask me to prove he is unable to dunk? Wouldn’t it be foolish for him to expect me to believe he can simply because I am unable to prove he cannot?
It is easy to prove a positive claim; all you have to do is demonstrate and your point is proven. But to prove a negative claim is often impossible; thus it is foolish to expect the two claims (positive claims vs negative claims) to be considered equal
I think we "prove negatives" considerably more than you realize. In the last week I realized I had quite a number of times which is what made me ponder on it a little more. I have kids and I am a software developer so trust me I can rattle off a tone of cases, and find plenty more outside of that too. Say in the case of software development when dealing with millions of lines of legacy code, you may need to conclude a bug does not exist, in some cases you may not be able to easily, since it is difficult to access all the code paths (or too time consuming so there is a trade off), so you infer from the evidence you do have. While there may not be complete certainty due to complexity (or worse technical debt which is often the case with legacy code), you are justified in believing that a bug does not exist , or no further ones have been introduced. And I most certainly don't say to my boss it's too hard so I can't prove a negative in those cases. Could you imagine what their response would be?
My boss would simply expect justification for my belief based on inferences from what evidence was accessible for that case.
In any case, just because you think it is almost "often impossible" or "too hard", doesn't mean one ought to hold to the belief "you can't prove a negative". You certainly proved that you could in your Santa Claus example.
And in the case where it isn't easy, you ought to have good reasons for why you believe ("the negative"), with what you do know, and come from that point. It doesn't have to be about absolute certainty.
I am sure when you said you had doubts about your friend, you could back it up with what evidence you did have and be justified in what you believed. For example, he was not as fit as he use to be, his eye sight was poor and he was fumbling the ball and so on.
Say I said to you I had a conversation with a stranger last week. And you said prove that stranger exists and what you said. Well could I easily in that case? What I would do is offer good reasons for it and/or find what evidence I could that could be inferred from. I could come up with stacks of scenarios like this. The "positive" can have same problems, as such you can't always easily prove a "positive" either. And given that it doesn't mean we are not justified in affirming the "positive" with what evidence we do have.
My point wasn't about absolutes Kenny, or which is "easier". My point is you can't say "we can't prove negatives" because we do, thus you might want to rethink that that claim.
The same rules apply to the existence of God, in that we work with what evidence we do have, but that is a discussion for another time.
