Sometimes it is easy to see what explains a supervenience thesis. Consider the examples of trivial supervenience relations from Section 3.5. It is obvious why there cannot be an A-difference without a B-difference if A is a set of necessary or impossible properties—namely, because there cannot be an A-difference at all. The supervenience relation is explained by the necessity or impossibility of the supervening properties. It is also obvious why A-properties supervene on A-properties. Of cours