A quote from Herb Silverman which explains atheism quite well.
Many people tell me they wouldn’t mind if I were an agnostic, but that I shouldn’t be so arrogant as to be an atheist.
I used to call myself an agnostic because I could not logically prove whether a god exists, so I took the agnostic position that the existence of any god is unknown — and perhaps unknowable. I was without belief in any gods and thought it highly improbable that any supernatural beings exist. When I learned that this view is consistent with atheism, I became an atheist.
So, my “conversion” from agnosticism to atheism was more definitional than theological. In reality, depending on how terms are defined and their context, I can accurately call myself an atheist or an agnostic, as well as a humanist, secular humanist, freethinker, skeptic, rationalist, infidel, and more.
I’m curious about why people find “atheist” so much more threatening than “agnostic” when self-described “atheists” and “agnostics” often hold identical views about deities. As with atheists, agnostics almost never give equal merit to belief and disbelief. For instance, I can neither prove nor disprove the following claims.
Claim 1: The universe was created 30 minutes ago and the creator planted false memories in all of us.
Claim 2: Infidels who don’t believe in the Flying Spaghetti Monster are condemned to burn for eternity in a vat of hot pasta sauce.
I assume we are all “agnostic” about these two hypotheses, but at the same time pretty certain they are false. (I’d also call myself an atheist with respect to such creators.) The burden of proof is on the person making the assertion — as it should be with any supernatural claim.