A recent exchange over on bookface:
Gary Hardcastle: Necessarily, there is no everything bagel. It would have to contain itself as an ingredient. But, I can buy one at the deli.
P.D. Magnus: A bagel always trivially includes itself.
GH: That way lies madness.
PDM: Take an empty bag. Put a bagel in it. There is nothing in the bag now that was not an ingredient of the bagel. Since the bagel is in the bag, it follows that the bagel too is an ingredient of the bagel.
I feel like I should drop a QED at the end of that, but I also feel like this is the kind of dispute which would get one of us excommunicated if we were medieval monks.
And that’s why I’d make a bad monk.