Well, they have already told us:
"Definitions
Atheism is the comprehensive world view of persons who are free from theism and have freed themselves of supernatural beliefs altogether. It is predicated on ancient Greek Materialism.
Atheism involves the mental attitude that unreservedly accepts the supremacy of reason and aims at establishing a life-style and ethical outlook verifiable by experience and the scientific method, independent of all arbitrary assumptions of authority and creeds.
Materialism declares that the cosmos is devoid of immanent conscious purpose; that it is governed by its own inherent, immutable, and impersonal laws; that there is no supernatural interference in human life; that humankind, finding the resources within themselves, can and must create their own destiny. It teaches that we must prize our life on earth and strive always to improve it. It holds that human beings are capable of creating a social system based on reason and justice. Materialism’s ‘faith’ is in humankind and their ability to transform the world culture by their own efforts. This is a commitment that is, in its very essence, life-asserting. It considers the struggle for progress as a moral obligation that is impossible without noble ideas that inspire us to bold, creative works. Materialism holds that our potential for good and more fulfilling cultural development is, for all practical purposes, unlimited."
We envision a world in which policies are made using the best evidence we have rather than using religious dogma.
www.atheists.org
So I don't have to ask them.
And have I made this up?