Atheism is a broad based brush.
Some atheists are all for reason. They will freely admit, without evidence one way or the other, they cannot commit to a belief a deity does exist, and they cannot commit to a belief that a deity doesn't exist. These atheists carry a belief, there isn't enough evidence to supply a credible answer. It is a belief pattern.
Other atheists are not so reasonable. These are the mirror image to the theists, creationist. They are beyond reason and for which reason I have dubbed them the extremist irrationalist. Their belief is, Deities do not exist, and have never existed, and is just a figment of a persons imagination. To this endeavour they point to their evidence of Evolution, physics and selected choices as it pertains to psychology and other brain related sciences. They cling to anything, so long as it proves their belief pattern right. It is a belief pattern.
Atheism is a belief pattern like any other.