I explore the regions of quark masses where CP will be spontaneously broken
in the strong interactions. The boundaries of these regions are controlled by
the chiral anomaly, which manifests itself in ambiguities in the definition of
non-degenerate quark masses. In particular, the concept of a single massless
quark is ill defined.Comment: 9 pages, 5 figures, contribution to the 6th Conference on Quark
Confinement and the Hadron Spectru
