 To say that a law is a universal truth having explanatory power is like saying a chair is a breath of air used to seat people. You cannot make a silk purse out of a sow’s ear, not even a very good sow’s ear; and you cannot make a generalization, not even a purely universal generalization, explain its instances. The fact that every F is G fails to explain why any F is G, and it fails to explain it, not because its explanatory efforts are too feeble to have attracted our attention, but because the explanatory attempt is never even made … Subsuming an instance under a universal generalization has exactly as much explanatory power as deriving Q from P &amp; Q. None (1977, 26).