Some philosophers regard no reducible physical properties as perfectly natural. However, in scientific practice, some but not other reducible physical properties (such as the property of having a given center of mass) denote genuine, explanatorily potent respects in which various systems are alike. What distinguishes these natural reducible physical properties from arbitrary algebraic combinations of more fundamental properties? Some philosophers treat naturalness as a metaphysical primitive. However, this chapter I suggests that it is not—at least, not as far as the naturalness of reducible physical properties is concerned. Roughly speaking, it is argued here that a reducible physical property’s naturalness is grounded in its role in the explanation of laws.
