Thanks - I only just realized I didn't understand this, when I thought about it. I'm rather gratified that the answer isn't simple and obvious; I didn't underst

Thanks - I only just realized I didn't understand this, when I thought about it. I'm rather gratified that the answer isn't simple and obvious; I didn't understand it because it's beyond my intellectual capacity, not because I'm ignorant, and I think that's an OK excuse.