religionisbullshit.net

Many theists think that the existence of god is a priori, hence the reason they often ask atheists to "disprove" his existence, not realising that there is no need to disprove something for which no evidence exists in the first place. This is possibly why they often define an atheist as "One who denies the existence of God" - clearly absurd as one would have to believe in God in the first place to be able to then deny his existence.

Atheism actually has a very simple definition:

a [without] theism [belief in a deity]

Atheism is not a religion or a system of belief; it is merely the absence of a belief. The term "agnostic" is therefore meaningless, and anyone who does not actively believe in a deity can be called an atheist.

Of course many atheists go further than this and make positive statements like "there is no God". Such people are generally referred to as "strong" rather than "weak" atheists.

As a definition, the above should more than suffice. Unfortunately atheism seems to imply rather more than this to certain groups of people. I have written about this, along with some personal thoughts on the subject, in the next section (in which you can post comments).