Ah, I thought you were saying they were the same, my misunderstanding. I can see an argument that PZs are incoherent by construction, but I'm not sure why a PM

Ah, I thought you were saying they were the same, my misunderstanding. I can see an argument that PZs are incoherent by construction, but I'm not sure why a PM is. Can you explain why you think that is so?