| Not being an atheist this is a difficult question to answer. However, I will do my best.
Atheism is a theory which contends there is no God, or if there is he cannot have any influence in the material world. Atheists see the difficulties in proving the existence of God as a reason for not believing in God.
It is also helpful to understand the history of atheism. As science developed over the last couple of centuries more and more of the natural world was given over to a scientific explanation. It has now reached a stage where some people believe that science can explain everything, so God has been completely forced out.
As to whether atheists believe in souls; well I guess that depends on the atheist.
I tend to think that the majority of atheists do not because they don't or won't entertain any metaphysical arguments. | 
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