Definition of "atheism"

[Pyrrho]

Every form of theism involves a belief in the existence of at least one god.  That is the minimum requirement to be a theist of some kind.  There is no additional doctrinal requirement to be a theist.  Of course, to be a particular type of theist, like, say, a Southern Baptist Christian, then there are more requirements than just belief in the existence of at least one god.  But all people who believe in the existence of at least one god are theists.

For more on these topics:

http://en.wikipedia.org/wiki/Atheism

http://en.wikipedia.org/wiki/Theism

Would you say that God by definition includes "intellect" or "mind," or could someone say, "I believe in a first movent that 'causes motion that is eternal and does cause it during an infinite time,' and that is 'indivisible and without parts and without magnitude,'" and still disavow belief in God?

Capitalizing "God" (other than at the beginning of a sentence, of course) makes it different from not capitalizing it; it makes it a "supreme being" type of god.  See:

http://dictionary.reference.com/browse/god?s=t

But I am inclined to think that all gods have some sort of intellect or mind implicit in them.  Otherwise, what would be the difference between pantheism and atheism?

See:

http://dictionary.reference.com/browse/pantheism?s=t

http://en.wikipedia.org/wiki/Pantheism

So I think if you believe in a first cause that does not involve intellect or mind, then you are not believing in a god (at least not as the first cause).  The Big Bang theory is perfectly compatible with atheism, though it does not entail atheism.  Many theists believe in the Big Bang theory.