Mathematically, I guess the most general thing is we have some local constraints, like:
or
and then an argument that universal satisfaction of these local constraints implies that the problem is insoluble, and so a solution must imply that there is at least one place where a local constraint was violated.
Mathematically, I guess the most general thing is we have some local constraints, like:
or
and then an argument that universal satisfaction of these local constraints implies that the problem is insoluble, and so a solution must imply that there is at least one place where a local constraint was violated.