Disbelief or Lack of Belief?
Atheism has been defined as the disbelief or lack of belief in the existence of God or gods. On the American Atheists website (https://www.atheists.org) it says: "Atheism is usually defined incorrectly as a belief system. Atheism is not a disbelief in gods or a denial of gods; it is a lack of belief in gods." It also declares on their website that: "Atheism is not a belief system nor is it a religion."
It also states: "The only common thread that ties all atheists together is a lack of belief in gods and supernatural beings."
Ethics Without God(s)
Atheists maintain there is a standard of goodness independent of a God or gods. They believe Atheists must approach the problem of finding natural grounds for human morals and establishing a nonsuperstitious basis for behavior. Why the necessity to do so if theirs is just a "lack of belief in God or gods"?
It is claimed on this website that "it is in our natures to desire love, to seek beauty, and to thrill at the act of creation." In other words, "We do not need a God to tell us we need to be good people, we can decide that on our own, because it is part of our nature."
Thoughts to Ponder
If "atheism" was merely a "lack of belief in the existence of God or gods," one would have to ask then, is there any possible evidence that would cause them to start believing in a God or gods? What would it take? Judging by other things they say, it appears they have actually chosen to disbelief in a God or gods, and nothing would change their minds. Their "lack of belief" appears to be a clear choice, and not just for lack of evidence for the existence of a God or gods.
They Want to Define Themselves
I understand why atheists want to be able to define what their philosophical worldview is, and not want others to do that for them. On their website they state: "Why should atheists allow theists to define who atheists are"? They object to dictionaries that define "atheism" as "a belief that there is no God." They also object to dictionaries that describe an atheist as someone that says: "There is no God."
Final Concluding Thoughts
Saying atheism is not a "belief" or not a "religion" does not make it so any more than stating "there is no God" makes that the deciding factor in what determines reality.
What determines whether their position is a "lack of belief" or a choice to "disbelieve"? If it was just a mere "lack of belief" wouldn't that mean they would be open to change their mind if evidence would point to the existence of a God or gods? That clearly does not appear to be the case. Whether a God or gods do or do not exist does not seem to be the issue here.
Do creationists usually have a "lack of belief" in evolution; or do they usually have a "disbelief" in evolution? For whatever their reasons might be, I believe they have made a choice to disbelieve in evolution.
Do evolutionists usually have a "lack of belief" in biblical creation, or do they have a "disbelief" in biblical creation? For whatever their reasons might be it would appear that they have made a choice to disbelieve in biblical creation.
Is a creationist's disbelief in evolution because of their choice to believe in biblical creation? That could be the case. Is an evolutionist's disbelief in biblical creation because they have made a choice to believe in evolution? That could be true also. Is an atheist's "lack of belief" in the existence of a God or gods because they have made an intentional choice to "disbelieve" in the existence of a God or gods? Would it then not be best classified as a chosen disbelief in a God or gods? I guess it might depend on how you want to look at it.