An Anti-Reductionist’s Guide to Evidential Support

What sorts of properties should we use in building our conception of the way the world is? David Lewis offers one answer to this question; Robert Stalnaker offers another. Lewis suggests a reductionist picture, according to which we should strive to build our conception of the way the world is on the basis of fundamental (or ‘perfectly natural’) properties. Fundamental properties, according to Lewis, “render their instances perfectly similar in some respect. They are intrinsic; and all other intrinsic properties supervene on them.” Lewis is committed, moreover, to a supervenience thesis. He thinks that fundamental properties “figure in a minimal basis on which all else supervenes. No two possible worlds just alike in their patterns of instantiation of fundamental properties could differ in any other way.” See especially (Lewis 1983), (Lewis 1986b, introduction) and (Lewis 2009). Citations in this paragraph are taken from the latter. In the introduction to (Lewis 1986b), Lewis states a stronger version of the supervenience principle, and describes it as contingent. According to the stronger principle, no two possible worlds just alike in their spatio-temporal distributions of point-sized instantiations of fundamental properties could differ in any other way. The weaker principle I cite above appears in (Lewis 2009), and there is no indication that Lewis took it to be contingent.