[VadeRetro]

There has always been a question of "What exactly is mass?" There's this intuitive notion that some things are somehow "made of more stuff" than other things, just what the "stuff" stuff is is a puzzle.

(OK, now you try composing a sentence with "stuff stuff is is.")

[VadeRetro]

... just what the "stuff" stuff is is a puzzle.

'... but just what the "stuff" stuff is is a puzzle.'

Would help if my own sentence was grammatical.

[Physicist]

(OK, now you try composing a sentence with "stuff stuff is is.")

"Stuff, stuff,
'Is' is,
Oh, what a relief it is!"

(Picture Bill Clinton singing this while boinking an intern...)

[unspun]

(OK, now you try composing a sentence with "stuff stuff is is.")

That it dependes on what "stuff" stuff is is quite the enigma in these Churchillian Russian doll-like systems then eh? (Or so it so strongly seems and don't we wish this didn't have to call up images Clintonian?)

[PatrickHenry]

OK, now you try composing a sentence with "stuff stuff is is."

What I say is stuff your "stuff stuff is is" stuff, is that clear?