When people have pointed out the complete lack of evidence for certain claims, such
as the existence of gods, others have responded that the absence of evidence is not evidence
of absence. But is that always the case? One of the reasons why it's a rather weak objection
is that there are countless claims for which there may be no "evidence of absence". To
insist on believing all of these things merely because there's no evidence to the contrary
would be absurd, and to selectively believe in only some of them is simply arbitrary,
and shows that these beliefs have nothing to do with evidence in the first place. Beyond
that, the absence of evidence for gods can sometimes be considered evidence of their
absence, depending on the evidence we would expect to see if a certain god existed. For
some definitions of gods, this is a trivial matter. For instance, the evidence at hand
does not show that the world was formed in the span of six days. It does not show that
a massive flood covered the entire earth within human history. And it does not show that humans
were simply created without having evolved from any ancestors. Any god whose existence
would result in these things being observed can thus be ruled out, because the evidence
we would expect to see if these gods existed is absent. But there are also definitions
of gods which state that their existence would have no observable effect, and whether these
gods exist or not, the evidence would remain the same. In this case, the choice to believe
in such a god is, once again, not rooted in evidence. To argue about evidence in the face
of this belief would be pointless, and moreover, there's no reason for those who hold such
a belief to debate the evidence or the absence thereof when their beliefs have no basis in
it anyway. This demand for "evidence of absence" implies that no evidence is needed in order
to believe in something for which there is no evidence, yet evidence *is* needed in order
to *not* believe in something for which there is no evidence. This is precisely backwards
- if there is no evidence of something, no additional evidence is needed to simply not
believe in it. Here, the principle applies to itself: the absence of evidence of absence
is not evidence of the absence of absence. Another potential source of confusion is the
failure to distinguish between the absence of any evidence regarding a phenomenon, and
the absence of confirming evidence of a phenomenon. It's the difference between just not bothering
to look for something, and looking for it but not finding any evidence of it. If there's
only an absence of evidence because you haven't taken the time to search for it, then of course
that absence of evidence wouldn't mean anything. But if we do attempt to seek out confirming
evidence and still fail to find it, the evidence that we did acquire in the process is still
evidence, not an "absence of evidence". Evidence that does not confirm a given claim is evidence
nonetheless. To accept only confirming evidence as evidence, while ignoring all other evidence
by calling it the "absence of evidence", would be a mistake. If the presence of evidence
in favor of a phenomenon would lead us to believe in it, then why shouldn't the absence
of that evidence sway our beliefs in the other direction? Finally, it's important to note
that the absence of evidence cannot be treated as proof of absence. Just because there's
no evidence of something does not mean we can conclude with perfect confidence that
it doesn't exist. That would be an argument from ignorance. But the absence of evidence
can still be evidence. It may be weaker or stronger evidence depending on the validity,
accuracy and scope of our efforts to verify or falsify a certain claim, but it is evidence.
And because this is evidence and not absolute proof, it always leaves open the possibility
that new evidence could be discovered which would require us to update and change our
beliefs. Some people have taken this as a license to say that there might be evidence
of gods, and we just haven't found it yet. And that's entirely possible. But the possibility
that such evidence might be discovered some day is only fatal to the claim that this has
been definitively and permanently ruled out with total certainty. That possibility alone
does nothing whatsoever to undermine the fact that the evidence as it stands reflects the
nonexistence of gods and not the existence of gods. And insofar as we intend to base
our beliefs on evidence, this means using actual evidence and not imaginary evidence.
We work from the evidence we have, not the evidence we don't have. There's no point to
believing things that might be true if there were evidence of them. Our beliefs are sourced
from what we know is true because there's evidence of it. And sometimes, that evidence
is evidence of absence. The evidence for the absence of gods, even if you consider it to
be very weak, is still vastly greater than the evidence for the presence of gods. And
unless later findings should happen to alter this, it's plain to see where the evidence
is pointing us - assuming we care to follow it.