Grounding the Unreal

Louis deRosset (University of Vermont)

The scientific successes of the last 400 years strongly suggest a
picture on which our scientific theories exhibit a layered
structure of dependence and determination.  Economics is dependent
on and determined by psychology; psychology in its turn is,
plausibly, dependent on and determined by biology; and so it goes.
It is tempting to explain this layered structure of dependence and
determination among our theories by appeal to a corresponding
layered structure of dependence and determination among the
entities putatively treated by those theories.  In this paper, I
argue that we can resist this temptation: we can explain the sense
in which, \eg{}, the biological truths are dependent on and
determined by chemical truths without appealing to properly
biological or chemical entities.  This opens the door to a view on
which, though there are more truths than just the purely physical
truths, there are no entities, states, or properties other than
the purely physical entities, states, and properties.  I argue
that some familiar strategies to explicate the idea of a layered
structure of theories by appeal to reduction, ground, and
truthmaking encounter difficulties.  I then show how these
difficulties point the way to a more satisfactory treatment which
appeals to something very close to the notion of ground.  Finally,
I show how this treatment provides a theoretical setting in which
we might fruitfully frame debates about which entities there
really are.