Quark masses, chiral symmetry, and the U(1) anomaly

I discuss the mass parameters appearing in the gauge theory of the strong interactions, concentrating on the two flavor case. I show how the effect of the CP violating parameter $\theta$ is simply interpreted in terms of the state of the {\ae}ther via an effective potential for meson fields. For degenerate flavors I show that a first order phase transition is expected at $\theta=\pi.$ I speculate on the implications of this structure for Wilson's lattice fermions.