 The third observation I wish to make at this point is that Lewis is strongly motivated by a desire for theoretical economy—both with respect to ontology and with respect to ideology. His quest for ontological economy shows up in the austerity of the kinds of fundamental entities he admits into his ontology (he neither shows, nor cares to show, any economy with respect to their number). His quest for ideological economy shows up in several places, but perhaps most notably in his utter rejection of any unanalyzed modal notions, and—something that hasn’t been mentioned yet—in his attempted reduction of set theory to mereology and plural quantification.