Atheism is not an active disbelief, it is a passive disbelief, in that passive disbelief is the default state for any extraordinary claim that has no apparent and obvious evidence for it’s truth claim. (take a second to re-read that bit and understand it, it’s important)
One can however take the lack of apparent and obvious evidence for this extraordinary claim and say, based on this, that they believe that this claim is not true, however this is an active disbelief and is distinct from ‘textbook’ Atheism. Many among the atheist ‘community’ have described the difference between these two as being ‘weak’ and ‘strong’, the latter being an active disbelief, however this is unfortunately confusing and unclear for those who are unaware of this distinction and most uninformed people assume that Atheism is in fact an active disbelief, which is not the case.
It is from this lack of clarity in terminology that comes the claim from many religious people that atheists “have faith” in their atheism, or even worse, in science. This is not only intellectually dishonest, but it’s also based upon a mountain of bad inferences and terrible logic and again a lack of understanding where terminology is concerned.
Faith is belief without evidence. Science only takes seriously claims that display overwhelming evidence for their truth claim. Atheism is a lack of belief.. An active disbelief in the existence of God, or gods, is based (in the case of rational minds) on the lack of overwhelming evidence in favour of that truth claim. As such, atheism, even when it’s not correct to refer to it as such, is all about the evidence, as is science.
If there’s no evidence either way, then there’s no basis upon which to form a belief either way.