“No” to your first two questions. This has been explained many times on Quora. I’ll try again.
A number of points:
- “Agnostic atheist” is not an “affiliation” like “Roman Catholic” or Presbyterian” is an affiliation. It’s a description like “Christian” is a description.
- “Christian” describes a “Christ follower,” while “atheist” describes a person lacking beliefs in God or gods. “Non-theist” might be another term for atheist.
- “Agnostic atheist” describes an atheist holding a specific philosophy. Now-a-days, agnostic is understood to mean “not knowing whether God exists.” Originally. the word was coined to mean that it is impossible to know whether or not God exists. Logically, “agnostic atheist” can describe either of these two.
- Using either of the above (in No. 3) definitions for agnostic works for atheist agnostic. It describes a person who:
- lacks belief in God/god, and
- does not know whether God/god exists.
An agnostic theist is a theist (Christian, Hindu, etc.) who admits the impossibility of proving God/god’s existence but who never-the-less believes in God/god.
Some atheists think they know for sure that God/god does not exist. An agnostic atheist lacks belief (does not hold belief) in God/god. Agnostic atheists don’t think anyone can prove it one way or another. Never-the-less, they don’t believe in God/god. That makes them atheist.
See now why the “atheist” part is needed? To distinguish atheists from theists.