The combinatorics of n-categorical pasting (Q909013)

Pasting 2-cells in a diagram is a somehow obvious process on any simple concrete example you have in mind. When the diagram gets complicated and various horizontal and vertical compositions are mixed, you rapidly give up and write ``One proves easily that this defines a composite cell...'' Amazingly enough, the metatheorem everybody had in mind about pasting 2- cells was never proved before this paper, even if the attempts to do so were numerous. The present paper should therefore be considered as a central one in 2- category theory and even, more generally, in n-category theory, since this is the context in which the pasting theorem is proved. The paper is moreover very nicely written. It should be read by anybody using 2- categories.