Atheist, Deist, Agnostic
[This installment of the AO Dictionary was delayed by a sleeping librarian and a missing thesaurus. The Atheist claims that the thesaurus doesn't exist, the Deist says it does exist but left. The Agnostic says we'll never really know, and he doesn't really care.
Turns out is was being used by a Christian to write his article.]
Atheist
The atheist believes there is no God, or that there are no deities. It should be noted that a belief about the existence of God is the same field as any other belief about God – that is to say atheism is as much a religion as any other belief. Like any other belief about God, atheism cannot be proven scientifically.
Like other broad religious definitions, atheism can be further divided by beliefs. Some atheists believe that while there is no God, there are supernatural occurrences or phenomena. Other atheists believe that there is no God, and there are no occurrences that are outside the natural, material world. There are other atheistic beliefs that fall somewhere in between and around those two.
There are two basic ways to become an atheist. Some atheists reach that belief honestly, and their belief effects their worldview. Others reach it by necessity, they have a worldview that necessitates the absence of a God. For them their worldview effects their belief.
Deist
A deist believes that there is a God, that there is a deity. This is not the same as a belief in a supernatural. It is a belief that a being has created the natural, material world, not a belief that supernatural occurrences may happen outside the natural bounds of the material world.
However the deist believes that this creator set in order the universe and the natural laws that govern it, then removed itself from any further interaction. The deist views the creating deity as the first cause, but nothing more.
Agnostic
The agnostic believes that the existence or non-existence of God cannot be known. There is a stark – but perhaps subtle – difference between the belief of the agnostic and the fact that the existence of God cannot be proven or disproven scientifically.
The honest atheist must admit that atheism cannot be proven scientifically, but he will still claim to know – for reasons outside of science – that a deity does not exist. An honest Christian will admit the same. An agnostic will reject both, claiming that neither can claim to know they are correct.