When atheists debate with monotheists, the former give primacy to coherent rational argument whereas the latter give primacy to faith. Not everyone is open to being convinced by the tool of reason. So I advocate arguing against God worshippers by asking them to clarify their most fundamental beliefs, like 'God', 'soul', 'heaven', etc. Faith is camouflaged in a vagueness of language and monotheists declare their belief in things of which they have no comprehensible understanding, seemingly ignoring the cognitive difficulty entailed in this. But if what they are claiming to believe is actually cognitively impossible to believe, then they have a difficulty which appears to be insurmountable.
For example, when someone claims to believe that 'God is an uncaused entity' we should challenge them to clarify what they think this statement means. What kind of living creature can exist without being caused to exist? What is its nature? Please make the statement intelligible. Similarly, if someone claims that after their body dies they will live on eternally as an immaterial essence called soul, then they will need to have an intelligible idea of what souls are and how an immaterial thing can exist in order to be able to believe this. Otherwise they’ll have no meaningful understanding of what it is that they are claiming to believe. If theists have no coherent or comprehensible idea of what their own statements actually mean, then in what are they believing? In what do they have faith?
Then you can suggest to them that they do not really have any such beliefs at all because it is impossible to believe something without having some idea of what it is that is being believed. We cannot seriously be said to believe something unless we have an intelligible object of thought. This object of thought is the thing that is being believed. If this object of thought is incomprehensible to the believer, then they have no idea of what it is that they are supposedly believing. How is it possible for someone to believe something without having the least notion of what that belief is?
If God worshippers cannot comprehend what they mean by their own stated beliefs, then they literally have no idea what they are talking about. They do not believe what they claim to believe because it is cognitively impossible to believe it. They should either make these statements comprehensible or abandon them. —JP Tate