Grothendieck ( if it is him) said somewhere :

"This xxx is at least an idea that will not be used in physics".

Q1 : is ?? an n-groupoid , a stack  ? Can you supplies the precise quote ? (in French or in English it does not matter).

Q2: Predecessors in the same vein quotes would be of interest? Thank you.

Grothendieck (if it was him) said somewhere :

This XXX, at least, is an idea that will not be used in physics.

Q1 : Is XXX an n-groupoid? a stack? Can someone supply the precise quote, either in French or in English?

Q2: Predecessors of this quote in the same vein would also be of interest. Thank you.