exogeneity and spontaneity

"Exogenous shocks" play the same theoretical role in macroeconomics as "spontaneous symmetry breaking" does in particle physics.

• They are comical devices intended for covering up the severe short-comings of a theory that is supposed to be all-encompassing.
• They are devices whose mere existence is contradictory: There can be nothing exogenous to a macroeconomic system, and there can be nothing spontaneous (un-caused) in a physical theory.