I haven’t thrown out the explanation in a while, so here is why I see Agnosticism and Atheism as two separate beliefs or viewpoints and why they don’t exactly overlap with each other or with Theism. I honestly believe it is a third and different viewpoint. Theism and Atheism deal with belief and Agnosticism deals with knowledge and hopefully my explanation with clarify this.
Theists have a belief in some sort of creator for the universe. Theists either have a somewhat exact view or at the very least a vague notion of what this creator is and the nature of that creator’s existence. A theist that qualifies their belief by saying they only believe and do not have actual knowledge are not agnostic. This uses the word agnostic as an adjective to qualify the theistic belief and not as a noun describing the overall viewpoint on creation.
Atheists are the opposite of theists by either actively rejecting the entire idea of a creator or at the least rejecting specific definitions of a creator as defined by theists. An atheist that qualifies their belief by saying they only believe this because they lack knowledge is not an agnostic since they have a belief about creation. This is also using the word agnostic as an adjective to qualify their atheistic belief and not as a noun describing their viewpoint on creation.
We now move from belief to knowledge.
Gnostics have a belief in a creator and the name is derived from the greek word for knowledge. They apparently made claim to know things that others simply had a belief in. It is from this word that Huxley came up with the idea for the word agnostic to describe his lack of knowledge for such things as creation.
Agnostics do not have a defined belief in regards to creation because agnostics do not know. Agnostic means “without knowledge.” An agnostic cannot be a theist because they can’t have a belief in something that they do not have a knowledge of. You cannot believe in the undefined. As soon as the belief takes on any vague definition of a creator then they are a theist (albeit an agnostic theist) and not an actual agnostic.
An agnostic is not exactly an atheist in the strictest sense since an agnostic can’t completely lack a belief in the creation concept in general. This is because an agnostic does not know the nature of the origins of the universe and does not have knowledge to reject such a concept overall. An agnostic’s lack of knowledge does align them with weak atheism in that they must agree in the rejection of theistic definitions since the agnostic believes in the fact that we do not know. This rejection is based on a lack of knowledge, not a specific knowledge or active belief that such things are wrong.
In short, the agnostic sees belief for or against the idea of a creator as wrong because we lack the knowledge to believe in such things as well as the knowledge to completely reject the entire idea of a creator. The agnostic doesn’t jump into the spectrum of belief or complete disbelief in a creator and says they don’t have the knowledge to put themselves on a point of the line for that scale. It is not done to sit on a fence on the subject but just to simply say they are not in the fight for or against belief and anyone engaging in such a fight is doing so from a position of complete ignorance.
I also don’t believe that I lack this knowledge because I’m unwilling or not open to a knowledge that is attainable. I believe such knowledge and concepts are beyond human understanding and ability. I seriously doubt that we can become capable of understanding the true origins of the universe.
If you take the Schrödinger’s Cat thought experiment and apply it to belief then the cat is god. Theists believe the cat is alive, atheists believe the cat is dead, and agnostics claim not to know that a cat is even in the box and leaves it open to suggest that it could be a dog, a unicorn, something we’ve never encountered before in this universe, or simply nothing at all that we’re arguing about. Without having knowledge of what’s really in the box and believing that we shouldn’t rely on Schrödinger to tell us, unknown can be the only correct answer.