Originally posted by Soylent Green Is People
For the record, I personally believe that other intelligent life almost surely exists elsewhere in the universe, but I don't presume or project the
reasons behind my belief as being "Proof". It is simply evidence, and circumstantial evidence at that. I think that evidence is overwhelming in
favor of life being elsewhere, but it isn't proof.
I'd agree with that. But in general, I'd just be careful with demands for 'proof' in the empirical world.
Even if you thought you had "proof," that would still just be a justified belief that you assumed
was true - new physical evidence could
always arise that would overturn what you thought with certainty was true. In other words, we're always dealing in probabilities.
There is no absolute certainty when it comes to inferences dealing with the empirical world because there is always the chance that counterevidence
will arise. The empirical world is 'fuzzy' and our perceptual and belief faculties subject to error, no matter how certain we think we are. So to
demand 'proof' in the empirical world is to me a misnomer. You can demand evidence
, but not proof. When people demand 'proof' for things
like alien life, they seem to be demanding something that would entail, with absolute certainty, that life elsewhere exists. But that
'proof' is only found in logical or mathematical deductions.
But notice how even Euclid's geometrical proofs that we'd accepted for hundreds of years as absolutely certain were later discovered to rest of
fallacious assumptions - in particular, the parallel postulate (axiom). The parallel postulate seemed so obvious that no one questioned it, until
Lobachevski realized that it rested on an even deeper assumption - that of the structure of Euclidean space (based on the idea of flat,
two-dimensional planes). But if you assume a different underlying spatial structure, like the surface of a 'saddle' (as in Lobachevski's
hyperbolic geometry), the parallel postulate fails because there exists more
than one line that passes through an external point (not on that
line) that doesn't intersect that line.
In other words, what seemed
to be an obvious and valid proof actually rested on further underlying assumptions that no one realized for over a
thousand years. In other words, even what seems to be a totally rigorous and obvious proof can be overturned based on new information. This is to
say that demanding absolute 'proof' might not be a reasonable thing to ask for, especially
when it comes to the empirical world. That's why
it's advisable to avoid demands for 'proof' when dealing with the empirical world, and to deal more in degrees of justification for belief, which
can be ascertained through higher or lower probabilities with arguments by induction. And even in those cases, with very high degrees of probability
on our side, we still could be wrong. On the other hand, it's more likely to be true.
So instead of claiming 'proof' or demanding 'proof', I think it makes more sense to present or demand an argument based on evidence or
probabilities. It seems like people like to cower behind the concept of 'proof' as a means of not having to engage with the actual arguments that
people are making. Let's just all agree that there will never be 'proof' in the sense of the absolute certainty of a logical deduction. Instead,
it would be better for someone who disagrees with the OP's argument to explain how high the probabilities would have to be in order for them to feel
as though they were justified in such a belief. And then we can talk about whether or not such demands are or are not unreasonable, maybe based on
everyday analogies that we're more familiar with.