That's not a "kind" of evidence -- that's all evidence.
It's not what you've been talking about.
The problem is that it can include just about anything,
Exactly. That's the problem.
In most cases, we have to look at both quantity and quality of evidence both for and against the assertion in order to come to some sort of conclusion about the truth of the assertion. Unfortunately, that evaluation is rarely objective.
Perhaps it is rarely objective. But I'm going to make a strong claim here. I'll concede that there may not be an objective means of ruling on evidence, but I most certainly do not concede that legitimate means of ruling on evidence is
arbitrary.
In other words, given two non-specific means by which one can rule on the quality and quantity of evidence, it does
not follow from "it is rarely objective", that these two means are equivalent, or equally valid, or equally sound--or, more to the point, equally rational. They may be. They may not even be comparable. But there are means of judging evidence that
are comparable, and not all means of judging evidence are equal.
Now I'll simply ask the question--do you agree?
Neither are particularly compelling, but scenario B is less compelling than scenario A in my opinion.
That's a start. Can you tell me why you hold this opinion then? What's wrong with B? What
feels wrong about it? What is it about this piece of evidence that makes it not count?
Note that evidence "1" in both scenarios is merely a proxy. We're really comparing A.2 with B.2. The only reason 1 is there is to keep you from backsliding into the red herring of compelling evidence, since it's
solely the
quality of evidence that is under discussion, and not the quantity, nor the overall judgment.
I agree, the coin flip probably isn't evidence of the assertion at all.
So at the very least, you should contend that there's stuff that can be proposed as evidence that has zero evidential value--and stuff that has more than zero evidential value. And there's a definite difference--after enough sunrises, after all, "the sun rose yesterday" definitely does contribute to your belief that it will rise tomorrow, but "the coin landed heads" never does.
So if these pieces of evidence ipso facto have this quality of potential value, do they not hold this quality, even when they stand on their own? Can't we say that the coin flip simply doesn't count,
before we even
consider that there may or may not be enough other evidence to push us over the edge? And that the fact that the sun rose yesterday
does count?
Sure, it might count as extremely weak evidence of aliens, as might the existence of teapots count as extremely weak evidence of teapots orbiting Jupiter, as might the fine-tuning of the universe count as extremely weak evidence of a god.
No no no no no! Those three things do not compare. In fact,
all three of them are different
from each other:
- Existence of intelligent life in the universe is beyond question. We definitely came to exist--this proves that intelligent life can exist beyond all reasonable doubt. All that has to happen for intelligent life to be elsewhere is for the same mechanisms to happen somewhere in the 100 nonillion cubic light years of the universe, again.
- Teapots also exist, beyond question, but by a known mechanism. In order for teapots to orbit Jupiter, either they would have to be put there, into the minuscule fraction of possible positions and trajectories that are describable as "orbiting Jupiter", which requires tremendous effort, or there would have to be an unknown mechanism that we have no reason to suspect exists, that would put them there.
- The fine tuning (proper) of the universe is theoretical, and suggests nothing about why the parameters happen to be such that life is supported, or even how likely it is in the first place, nor is it even comparable to a hypothetical entity's probable existence.
Sure, they're all the same in that they aren't compelling evidence of respective claims, but you're slipping back into the irrelevant. They are all different in quality. Without further argumentation, you can't judge on even the
improbability of extra terrestrial intelligent life--that we know for damned sure we exist at all lends a high degree of plausibility that it could exist elsewhere. Of course, you would note, rightly so, that we also can't judge in itself the
probability that there's intelligent life elsewhere, because that's extrapolating from a single data point--but you lack standing to argue specifically that it is
improbable; extrapolation is extrapolation is extrapolation.
The teapot orbiting Jupiter we can pretty much immediately start out with as unlikely. It's really a biased example, so it shouldn't surprise us--after all, we, intelligent life, which we're fairly sure isn't independently elsewhere in
the solar system, are the producers of teapots, and we're fairly grounded, so it's just an ordinary, anthropocentric example--were we to consider a rock orbiting Jupiter, it would be different.
And as for the argument for God, we're not even out of the ontology box... we've yet to establish that there's even an existing entity of the class in the first place. The fine tuning argument doesn't even establish this--it requires you to interject a prior, which is
entirely up to the opinion of the theist going through the exercise or the atheist debating her. We know damned well intelligent life exists. Hell, we even know damned well teapots exist. Gods? Well, you sort of "need" faith, right?
In other words, there is not compelling evidence for any of those assertions.
Which is not interesting.
All might also count as very strong evidence in conjunction with other evidence, particularly other pieces of the puzzle which are currently missing.
But they are vastly different in
quality. See above--evidence can be judged in terms of its quality in support of a claim aside from judgments of whether or not the totality of the evidence supports the claim.