This question teaches us something about how formal reasoning does and doesn't work, and does and doesn't correspond to common-sense ideas like "supporting evid

This question teaches us something about how formal reasoning does and doesn't work, and does and doesn't correspond to common-sense ideas like "supporting evidence" and "relevant". Then you might ask, why do we care about how formal reasoning works? Because the alternative, common-sense reasoning, works really well up to a point, after which it fails badly.