Many Atheists will say they believe in the primacy of science for explaining the world. It might be more correct to say that atheists are really doubters of established traditions, favoring instead looking for new explanations of the world through new methods and technologies.
Some high profile atheists, or “Evangelical Atheists” such as Richard Dawkins and Christopher Hitchens spend their lives writing books and debating with believers attempting to convince them that the beliefs of yesteryear have been disproved by scientific theory and should be discarded by the wayside along with other mythical beliefs such as the Roman and Greek gods.
The biblical creation story is one area where atheists are very quick to jump on believers. When taken literally it seems impossible given science’s current understanding of evolution that the world we live in could have been created in seven 24 hour days, only six thousand years ago. When they approach the issue in this manner, the atheists are only attacking one small subset of Christianity that could be termed young earth creationists. Young earth creationists are most likely among the minority of Christian believers, a sub group often called fundamentalists.
The previous paragraph illustrates a problem that Atheists have when describing what they believe. They are not putting forth a belief system at all, but attacking another belief system. It makes as much sense as Christianity attacking Muslims as incorrect in doctrine. Attacking the beliefs of another is not a belief at all, but a tactic towards minimizing those who are seen as the enemy.
Atheists also have the problem, that once they organize in any fashion they have to establish tenets of belief. Once a tenet or doctrine is established, a test begins to form to those who are faithful to the established doctrine, and those who are on the outside. If we could look forward a hundred years we might see the atheist groups of today, established as religions in the future. Their systems of belief and worldviews may be different than how we define religion today, but they will be religions none the less.
It seems clear that Atheism is not a position of belief, but of approach to the world. It is an approach that eschews tenets and doctrines in favor of enriching the body of human knowledge. It will never establish itself as a religion, because the minute it does, true atheism with reject the codification of a set of values as truth. Truth to the atheist is not determined by agreement or groupthink, but by the freethinker stretching to find a new and better way that does not stand on tradition and agreement.