Not believing in God is not a "belief" in itself.
People who don't believe in God argue that there is no proof of existence.
The simplest argument I can think of to demonstrate that their is no proof of God is...
Believers will claim that the complexity of Life on our planet shows that there must be an intelligent designer. However, by definition, that intelligent designer must therefore be more complex than that which he designed. Which mean that if complex life on our planet could not come about without a designer then our complex designer must also have had an even more complex creator. If you follow this back logically you get into an infinite loop of ever greater complexity.
The only way out of this loop is if you change the rules and decide to go the other way, starting with a simple source which becomes gradually more complex, which is the basis for evolution.
I accept that I will never know the true origins of life and how the universe came to be - I would love to know but I never will - and neither will any of us on here, religious or not.
It is technically possible that a God created the earth but I don't personally think it is the case. And if there is a God, I don't like him. Loo at the world. Christians claim that God is perfect and has perfect morals and perfect justice. Have you people read the bible or seen the news?