Should you answer a fool?

Let’s illustrate with an example.  Suppose you’re witnessing to someone, and you quote a Bible verse.  The atheist you’re talking to says, “You can’t use a Bible verse to defend your position.  You have to stick with hard evidence.”  Well, the atheist is trying to impose his reasoning on you.  He thinks that nature is all there is.  He doesn’t believe in the supernatural, and so he doesn’t accept your use of the Bible.

Some Christians might be tempted to stop quoting verses and shift to natural evidence only.  Although plenty of natural evidence certainly exists, you can’t let the atheist tell you how to reason.  You’ve let him bully you into reasoning according to his folly.  It just makes you look more foolish because you’ve come down to his level of arguing.  You’ve accepted his terms of argument, which are foolish.  You should avoid reasoning according to his folly.

However, you can certainly reason according to his folly for sake of argument.  For instance, you could reply, “You think nature is all that exists.  But can you tell me where the laws of logic come from?  Why is the universe so orderly?  If nature is all there is, and we came from an explosion, why is everything so orderly?  If nature is all there is, then you don’t have any free will, and you can’t even be sure you exist.  This could all be just an illusion.  Do you see how wrong your view is that nature is all that exists?”

Here, you reason with him according to his folly for sake of argument, showing him where his own reasoning leads.  But you should not use his reasoning yourself, or you will look foolish, too.