Originally Posted by Scott Alexander
Weak-manning is a lot like straw-manning, except that instead of debating a fake, implausibly stupid opponent, you’re debating a real, unrepresentatively stupid opponent. For example, “Religious people say that you should kill all gays. But this is evil. Therefore, religion is wrong and barbaric. Therefore we should all be atheists.” There are certainly religious people who think that you should kill all gays, but they’re a small fraction of all religious people and probably not the ones an unbiased observer would hold up as the best that religion has to offer.
If you’re debating the Pope or something, then when you weak-man, you’re unfairly replacing a strong position (the Pope’s) with a weak position (that of the guy who wants to kill gays) to make it more attackable.
But in motte and bailey, you’re unfairly replacing a weak position (there is a supernatural creator who can make people out of ribs) with a strong position (there is order and beauty in the universe) in order to make it more defensible.
So weak-manning is replacing a strong position with a weak position to better attack it; motte-and-bailey is replacing a weak position with a strong position to better defend it.