I understand what you're saying. I agree with most of it. I do
believe that one can argue that the existence of a god is unimportant/unnecessary (and very easily), but I do not
believe that one can argue against the existence of god without making the same faith based assumption, only to the opposite that there is not a god. Just because the existence of a deity is not necessary doesn't make it any more or less true. It just makes it unnecessary (as we have both said).
Also, might I ask where you are getting this definition from?
Atheism is the absence of belief in deities due to lack of evidence
So far as I can tell, Wikipedia, Google, OED, and Merriam-Webster all use the definition that atheism is the belief that there is no deity.
Hi there, I'm here to clear up some definition confusion.
First off, belief vs knowledge: Belief and knowledge lay on a continuum, with belief being on the less certain end of the spectrum and knowledge being on the more certain end of the spectrum. Belief and knowledge have nothing to do with what is true, because even knowledge may be mistaken.
Because they lay on a continuum, they can mean different things to different people. Remember this, because this becomes important later.
When someone says that they believe there is no god, they are asserting that they simply do not find the arguments for the god concept to be particularly convincing. When someone says that they have knowledge that there is no god, they are asserting that they have reason to believe that the given argument for the god concept to be flawed in someway, either with respect to logic or faulty assumptions or something else.
Depending on the god, it's possible to be more certain or less certain about belief. For instance, with respect to the Christian God as literally described by the Bible, I have knowledge that such a story does not square with reality, so I can say that I have knowledge that such a God (as describe literally by the Bible) does not exist. On the other hand, with respect to a more liberal interpretation of the Bible, as most moderate Christians have, it's much more difficult to be certain about the concept, in part because not all Christains believe various parts of the Bible are literal or allegorical, and which parts depend on the person.
If you're attempting to be pedantic, please stop. These questions are hard and complicated, and pulling out the dictionary and saying "see! it says belief right there!" is not helpful. The nature of language is complex and not everything means exactly the same thing to everyone else. That's why legalese is pretty much its own language. It's an attempt to shoehorn a very inexact and fuzzy system (standard English) into a very strict and regimented domain.
The purpose of dictionaries is an anchor affect, to prevent meanings from drifting too much, so everyone knows what everyone else is saying. However, they are not authoritative, and should not be taken as such. OED or MW do not have monopolies on the English language. If you're uncertain about a definition, then what you should be attempting to do is reconcile your definitions with the other party, and find a definition that you can both agree on. Reconcile the minutae that the dictionary writers never intended. Invent words if you must. English is a tool to be brought to bear on a discussion and elucidate your meaning, not a prison in which to confine your (or more dishonestly, your opponent's) thoughts and intentions.