There are at least twelve major virtues of good theories: evidential accuracy, causal adequacy, explanatory depth, internal consistency, internal coherence, universal coherence, beauty, simplicity, unification, durability, fruitfulness, and applicability. These virtues are best classified into four classes: evidential, coherential, aesthetic, and diachronic. Each virtue class contains at least three virtues that sequentially follow a repeating pattern of progressive disclosure and expansion. Systematizing the theoretical virtues in this manner clarifies each virtue and suggests how they might have a coordinated and cumulative (...) role in theory formation and evaluation across the disciplines—with allowance for discipline specific modification. An informal and flexible logic of theory choice is in the making here. Evidential accuracy, according to my systematization, is not a largely isolated trait of good theories, as some have made it out to be. Rather, it bears multifaceted relationships, constituting significant epistemic entanglements, with other theoretical virtues. (shrink)

This article presents a novel argument against a common principle of parsimony in philosophy. First, it identifies a widely employed principle of positive ontological parsimony, according to which we should, ceteris paribus, prefer smaller ontologies to larger ontologies. Next, it shows how this principle is used as part of a strategy by which to argue for antirealist positions in many subfields of philosophy: the ockhamistic antirealist strategy. Third, it argues that this principle commits its adherents to an implausible epistemological thesis—the (...) Eroding Ontology Thesis—according to which evidence for the existence of some entity is at least prima facie evidence against the existence of all other entities. Antirealists might decide to adopt a related position, ontological conservatism, according to which we should simply resist changing our ontology, but the article shows that it is independently unjustified. Therefore, it concludes, philosophers have good reason to cease employing one very common antirealist strategy. (shrink)