While I do not believe that everyone who has yet to draw a line in the sand is an atheist or agnostic, I do believe that there is a type of “default” belief when one consistently refuses to investigate and seek out the truth.
We all believe in something, most likely because we were raised in that belief. However, when we grow older and seek to confirm the authenticity of our belief, that belief provides the basis of our search for truth. We may be seeking to prove our religion true or false, but in so doing we are either holding to it or rejecting it for another belief as we investigate.
An Atheist believes that there is no supernatural Being, no God.
An Agnostic is one who believes that we cannot know anything definitive about God, his nature and being. Pantheists hold the belief that God exists within everything (in the Universe) and everything is God, or a part of “God.”
The Theist believes that a supernatural God exists and the identity of this God and the degree to which he is involved in the Universe determines the exact system of belief which the Theist will call his / her own. For example, a Deist acknowledges that a God exists but asserts that our existence is either beyond his control or his concern.
There exists no objective seeker who faces life with a blank slate.
One may be a skeptic, investigating all of these things, but all of us have a foundation of one belief or another – whether we claim it as our “religion” or not – from which we evaluate the truth claims of other religions. We can agree to set aside certain assumptions in order to be more objective but we will always compare what we are learning with what we have always known. There will always be certain questions that our foundational belief will require us to either answer or set aside as negligible. At some point in our lives, we may decide that another religion has more substantial truth behind it than the one which we have previously held to be true, but we are never without a belief.