and the foundations of methodological naturalism. To avoid getting lost on the way, some
preliminary remarks about terminology are needed.
Terminology
Let us call the domain of the natural sciences—a domain that includes stars and planets,
living beings and nonliving objects, stable entities—and ephemeral events, physical
objects and embodied mental and cultural entities—the natural world.
—Willem B. Drees, 1996
Nature and the Supernatural
We can define the supernatural in terms of the natural as follows:
x is supernatural =df. x is not a part of nature and x can affect nature.^2
This definition is adequate, however, only if a tolerably clear definition of “nature” can
be provided. It is not easy to find such a definition. “Nature” or “the natural world” is
sometimes defined circularly as “the domain of the natural sciences.” But while the
circularity of this definition can be eliminated by replacing “natural sciences” with
something like “biology, chemistry, and physics,” the definition remains obscure, in part
because it is far from clear what exactly the domains of those sciences are. Indeed, some
entities, like conscious states and political systems, are thought by many to be a part of
nature though not the proper object of study of any of the natural sciences.
Let us start by assuming that many of the entities currently studied by physicists and
chemists are real, and let us call these entities “physical” entities. Notice that this is a
very narrow, technical sense of “physical,” one that separates the physical from the
biological, the mental, the political, the social, the religious, the economic, and so on. If
we assume that whatever else nature includes, it includes atoms, molecules, gravitational
fields, and any other entities that are physical in this narrow sense, then the problem of
how to define “nature” boils down to the problem of how an entity that is not physical
must be related to physical entities in order to count as natural. Perhaps this problem can
be solved by noting that many of the nonphysical entities that we would want to count as
natural (e.g.,
end p.277
bacteria) are causally reducible to physical entities in the sense that their causal powers
are entirely explainable in terms of the causal powers of those entities. This suggests that
an entity can be classified as natural just in case it is a physical entity or is causally
reducible to physical entities.