vibratetogether wrote:
How do you deal with someone who insists on defending a position that has no defense?
Poke holes in their theory until it sinks. If it doesn't sink, maybe your estimation of the position wasn't as good as you thought. If it sinks and they realize it, you've won, and they will have to find a new position. If it sinks and they don't realize it, there's not much you can do. You can't physically force someone to think logically.
Sometimes, you'll be in the position where both sides think the other side has no defense, but they're both wrong about that. If both sides try to poke holes, they'll have an argument (possibly heated), but they might get somewhere. If both sides simply sneer and declare victory, they'll both insult each other for being stupid, and not get anywhere.
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"A dead thing can go with the stream, but only a living thing can go against it." --G. K. Chesterton