 Many features of the systems approach are appealing. For one thing, it deals with a challenge posed by vacuous laws. Some laws are vacuously true: Newton’s first law of motion — that all inertial bodies have no acceleration — is a law, even though there are no inertial bodies. But there are also lots of vacuously true nonlaws: all plaid pandas weigh 5 lbs., all unicorns are unmarried, etc. With the systems approach, there is no exclusion of vacuous generalizations from the realm of laws, and yet only those vacuous generalizations that belong to the best systems qualify (cf., Lewis 1986, 123). Furthermore, one goal of scientific theorizing is the formulation of true theories that are well balanced in terms of their simplicity and strength. So, the systems approach seems to underwrite the truism that an aim of science is the discovery of laws (Earman 1978, 180; Loewer 1996, 112). One last aspect of the systems view that is appealing to many (though not all) is that it is in keeping with broadly Humean constraints on a sensible metaphysics. There is no overt appeal to closely related modal concepts (e.g., the counterfactual conditional, causation, dispositions) and no overt appeal to modality-supplying entities (e.g., universals or God; for the supposed need to appeal to God, see Foster 2004). Indeed, the systems approach is the centerpiece of Lewis’s defense of Humean supervenience, “the doctrine that all there is in the world is a vast mosaic of local matters of particular fact, just one little thing and then another” (1986, ix).