  The strong CP problem is that SU(3) gauge field instantons naturally induce a
CP violating term in the QCD Lagrangian which is constrained by experiment to
be very small for no obvious reason. We show that this problem disappears if
one assumes the existence of at least one black hole somewhere in the universe.
The argument is reminiscent of Dirac's argument for the quantization of charge,
in which the existence of one monople anywhere in the universe suffices to
require the quantization of electric charge everywhere.
