 The criticisms leveled at the Extensionist and Dispersal theories follow a pattern that is characteristic of situations in which one theory is more ontologically parsimonious than its rivals. In such situations the debate is typically over whether the extra ontology is really necessary in order to explain the observed phenomena. The less parsimonious theories are condemned for profligacy, and lack of direct evidential support. The more parsimonious theories are condemned for their inadequacy to explain the observed facts. This illustrates a recurring theme in discussions of simplicity—both inside and outside philosophy—namely, how the correct balance between simplicity and goodness of fit ought to be struck. This theme takes center stage in the statistical approaches to simplicity discussed in Section 5.