My definition of a stupid person: A stupid person is a person who treats a smart person as though they're stupid.
(Clearly this isn't an actual definition, but it works pretty well if you reframe it as evidence rather than as a necessary or sufficient condition.)
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.