Grounding Explanations

A compelling idea holds that reality has a layered structure. We often disagree about what inhabits the bottom layer (or even if there is one), but we agree that higher up we find chemical, biological, geological, psychological, sociological, economic, etc., entities: molecules, human beings, diamonds, mental states, cities, interest rates, and so on. How is this intuitive talk of a layered structure of entities to be understood? Traditionally, philosophers have proposed to understand layered structure in terms of either reduction or supervenience. But these traditional views face well-known problems. A plausible alternative is that layered structure is to be explicated by appeal to explanations of a certain sort, termed grounding explanations. Grounding explanations tell us what obtains in virtue of what. Unfortunately, the use of grounding explanations to articulate the layered conception faces a problem, which I call the collapse. The collapse turns on the question of how to ground the facts stated by the explanations themselves. In this paper I make a suggestion about how to ground explanations that avoids the collapse. Briefly, the suggestion is that the fact stated by a grounding explanation is grounded in its explanans.