ABSTRACT
Many philosophers have held, in the tradition of Plato and Aristotle, that there are
uniquely philosophical, non-empirical methods of inquiry and that there are things
whose investigation is reliably conducted via such methods. Rejection of any such
methods or any such objects other than those available to sense experience or
scientific methods traces back to the monism of the presocratic philosophers. Call any
position entailing such a rejection “philosophical naturalism.” (At times we will simply
call such a position “naturalism,” for short.)
Philosophical monism in general, including idealism as well as materialism,
demands a single standard in metaphysics or epistemology, contrary to pluralism in
metaphysics or epistemology. Explanation in philosophy and science is inherently
unifying, subsuming a multiplicity of phenomena under classificatory unity – for
example, under a unifying cause in the case of causal explanation. Explanation
contributes unity and thus organization to what may otherwise appear as mere
diversity. Proponents of monism, however, must attend to the risk of neglecting
genuine data and truths resistant to a monistic explanatory scheme. What monism
gains by unification of multiplicity in data may be lost by neglect of genuine
recalcitrant data. Explanatory unity may be a virtue, but it will be virtuous only if
pertinent truths and data are not excluded for the sake of theoretical simplicity. Since
naturalism is, as we will see, monistic in its implications for metaphysics or
epistemology, it faces the threat of neglecting genuine recalcitrant data.
