Jonathan Barker

When and why does awareness of a belief's genealogy render it irrational to continue holding that belief? According to explanationism, awareness of a belief’s genealogy gives rise to an epistemic defeater when and because it reveals that the belief is not explanatorily connected to the relevant worldly facts. I argue that an influential recent version of explanationism, due to Korman and Locke, incorrectly implies that it is not rationally permissible to adopt a “sparse” ontology of worldly facts or states of affairs. I then propose a new explanationist account of genealogical defeat capable of accommodating rational belief in ontological sparsity. According to my account, awareness of a belief’s genealogy gives rise to a defeater when and because it reveals that the belief is not explanatorily connected to its truthmaker.

A fundamental fact is “pure” just in case it has no grounded entities—ex. Tokyo, President Biden, the River Nile, {Socrates}, etc.—among its constituents. Purity is the thesis that every fundamental fact is pure. I argue that Purity is false. My argument begins with a familiar conditional: if Purity is true, then there are no fundamental “grounding facts” or facts about what grounds what. This conditional is accepted by virtually all of Purity’s defenders. However, I argue that it is also the first step toward Purity’s undoing. For, if every grounding fact has a ground, then some grounded entities have “groundmates” or distinct grounded entities that share their full grounds. But, if there are groundmates, then Purity is false. So Purity leads to a contradiction. Therefore, it is false. I close by noting that my argument against Purity also gives us a powerful reason to think that some grounding facts are fundamental.

According to the Ontological Innocence Thesis (OIT), grounded entities are ontologically innocent relative to their full grounds. I argue that OIT entails a contradiction, and therefore must be discarded. My argument turns on the notion of “groundmates,” two or more numerically distinct entities that share at least one of their full grounds. I argue that, if OIT is true, then it is both the case that there are groundmates and that there are no groundmates. Therefore, so I conclude, OIT is false. Moreover, once we have seen why OIT is false, only three heterodox views about reality's structure remain. So this paper’s second conclusion is that, even after we have discarded OIT, we are in for an additional surprise.

I argue that one’s views about which “metaphysical laws” obtain—including laws about what is identical with what, about what is reducible to what, and about what grounds what—can be used to deflect or neutralize the threat posed by a debunking explanation. I use a well-known debunking argument in the metaphysics of material objects as a case study. Then, after defending the proposed strategy from the charge of question-begging, I close by showing how the proposed strategy can be used by certain moral realists to resist the evolutionary debunking arguments.