  Many philosophers follow Quine by citing a standard cluster of principles putatively constitutive of scientific standards: empirical adequacy, ontological economy, simplicity, fertility, and so on (Quine 1955, 247; Quine and Ullian 1970, chapter 5). However, lists of this kind are unsatisfactory for several reasons.  For one thing, the principles come in different versions. Yet it is doubtful whether the general versions are the scientifically sanctioned ones. Some writers claim, for example, that scientific appeal to ontological parsimony does not extend to the postulation of abstract objects (Burgess 1998). Others maintain that scientific appeals to simplicity are not best captured by the utterly general slogan ‘Prefer any theory T1 to any less simple theory T2 (in this respect)’ (Paseau 2007). Moreover, lists of this kind do not tell us how to balance desiderata against one another.