Atheism is the lack of belief in the existence of God or gods, which can range from a simple absence of faith to a more active denial of deities. It is often distinguished from agnosticism, which is the view that the existence or non-existence of God is unknown or unknowable, and theism, which affirms the reality of God. Atheism is not necessarily a single, monolithic belief, but encompasses various stances on different kinds of deities.Â