[madnak]

[ QUOTE ]
Let me see if I understand this. You're saying reality is what actually happens, beyond our perception of the world. We may perceive a relationship and call it reality, but we don't really know whether it actually is reality. In the same way, mathematics is just our way of interpreting relationships.

[/ QUOTE ]

Basically, yeah. It's fine to say we "know" something is reality, but detach yourself from that if someone gets very philosophical on you. We have reason to believe, based on the observations we've made and the information we have, that this is reality, etc. It's all very academic, but it can be important - math isn't "true" so much as it's consistent. Of course, any sentient beings in the universe probably use systems of mathematics very similar to our own - it's just, remember that a diagram of the solar system isn't really the solar system. (That hardly means the solar system doesn't exist, though.)

If your goal is to convince the audience, or even to impress them or just appear credible, it's important to be in control of the discussion. Never let the theist take the reins - if he knows what he's doing, then he'll make things difficult for you, and if he doesn't he'll take you in circles. If you get stuck, sometimes asking questions is the best response - the person asking the questions is often perceived as being the one in control. If the theist demands to monopolize the conversation, give him enough rope to hang himself with. If you're out of your depth rhetorically, stick to logic.

And remember, you aren't making the claim that there is no God - he's making the claim that there is. This puts you in an advantageous position. There are dozens of mutually exclusive religious belief systems out there, and his agenda is to support his own system and only his own system. His arguments will reflect that. If he starts to get very general, making broad points that almost everyone agrees with, tighten things up and get more specific - show everyone that he's being vague.

Always remember, you don't have to defend your worldview - you aren't asking everyone to agree with every little thing you believe. But the theist is often doing exactly that, so all you have to do is expose him.