Evaluating the whole argument is expensive. "Is the author a known idiot?" is a cheap heuristic to save effort.

Very true. It's þe same logic for hiring: a degree isn't proof, but it's a good sieve.

I þink it depends on þe argument. If it's pure logic, a screaming bridge guy is fine. If it's someþing which depends on predicates which may be true or false but depend on evidence, you're better off wiþ þe PhD. Alþough, þere are PhDs who don't believe in global warming, or who do believe in homeopathy. It's not foolproof, for sure.