In this youtube video [below], Feynman is discussing how scientists develop and test theories. At 05:10 he says this:
“I must also point out to you that you cannot prove a ‘vague’ theory wrong. If the guess that you make is poorly expressed and rather vague and the method that you use for figuring out the consequences is rather a little vague, you’re not sure and you decide, ‘I think everything is because, it’s all due to muggles and muggles do this and that more or less’ so I can sort of explain how this works then you see that that theory is good because it can’t be proved wrong. If the process of computing the consequences is indefinite then with a little skill any experimental result can be made to look like an expected consequence.”
I had no idea muggles were the “widgets” of theoretical physics.
Feynman pronounced the word differently than most modern muggles pronounce it — he seems to be emphasizing that it’s a nonsense word — and it’s not clear how he spelled it, if he ever spelled it (transcriptions we have seen simply eliminate the word).
BONUS: An Abstruse Goose cartoon about wizards and mathematicians. (HT Bob O’Hara)