Atheism is defined as a lack of belief in the existence of a god or gods, and it does not inherently require a denial of God's existence. The discussion highlights the distinction between strong atheism, which asserts that no gods exist, and weak or implicit atheism, which simply lacks belief without making a definitive claim. Agnosticism is presented as a separate concept, focusing on the uncertainty of knowledge regarding God's existence. The conversation also touches on the idea that belief systems, including atheism, can be seen as spiritual beliefs, although they differ from traditional religions that involve dogma and faith. Participants debate the implications of definitions, with some arguing that atheism cannot be equated with agnosticism, while others suggest that the terms often overlap in common usage. The discussion emphasizes the philosophical complexities surrounding belief, knowledge, and the definitions of atheism and agnosticism, ultimately questioning the validity of claims about the existence or non-existence of God based on evidence or lack thereof.