I would like to speak on behalf of Atheism.
It hold's strong validity. It is not ALL knowledge, but is it nonetheless part of it. All things have truth, we just need to have the "stillness of mind" to realize it.
The atheists need no God or belief to know that they here and that they exist. To an atheist, that is all they Need to know. They believe in what is HERE NOW, but in "stillness of mind" you realize that That is all anything really is. Have you ever blacked out or been knocked unconscious? Do you remember how long you were blacked out for? When we lose that mind, time for us does not exist. You wake up feeling like you've lost not even a second. That in itself is sort of an unintentional "stillness of mind" of sorts that we have all experienced. Have you ever experienced the feeling of deja vu? Perhaps that's another form of "stillness of mind". When you were completely unconscious did you need to believe in God? Did the thought even cross your mind? Time is relevant only to those who need it. A tree or an animal neither knows nor do they need to know time, they are in the HERE NOW. An animal does not need a belief in God to exist, they merely exist. The need to believe in anything is something concocted in our minds by our own thinking that we "need" to know EVERYTHING. In "stillness of mind" we realize that we really need to know nothing in order to have everything become known to us. I don't need to believe in God to know that I exist. I know there is more out there than just myself as well. For an animal that has that "stillness of mind" any belief or notions of God become irrelevant. It just exists and survives not really needing to know.....WHY? They are merely content in their own existence, even if they don't even know what that "existence" is. There will always be more out there than what we know. In "stillness of mind" it is in the epiphany or realization of accepting simply that we ARE part of EVERYTHING. Nothing more. All that exists is ONE. When you take matter and energy down to it's core and simplest state of being comprised of basically everything that exists, we find that it is ALL the same. All energy and all forms of energy are simply, Energy. There is no "void" in space, we only perceive it as that. The Sun and the Moon affect us because we are ultimately the same and connected. It is ALL energy. Even though we retain our separateness and uniqueness, we are still connected. We are affected by the Sun and in some unknown way we affect it. We are only part of that something which is bigger than us. Ever wonder why so many different people claim to be Cleopatra or Napoleon, or another famous person in a past life? Because we ARE all ONE and the SAME. Different, yet the same. Our energy is their energy. Our essence is their essence. What made THEM is what makes US. Pure energy, ALL the same. Energy itself seems to have a "memory". Why? Then in all of THIS, do we really Need a God? I Don't think so. All we need is the"Stillness of Mind" to know we are ONE.
Maybe some of this did not make any sense at all, but in My "stillness of mind" it really does not matter. I AM PART OF ALL. The believing and the disbelieving, the knowing and the unknowing. It makes no difference, it's all in how your mind perceives it.