Materialism (or physicalism) can signify either a broad metaphysical view, or, more narrowly, a type of theory of mind. Metaphysical materialism is a specific kind of naturalism which contends that everything that exists is either physical or dependent upon the physical. Broadly understood, reductionist materialism maintains that everything is strictly physical; more narrowly, it maintains that the mind (at least) is purely physical. Nonreductive materialism also allows the existence of nonphysical properties that inhere in, or emerge from, a physical substrate. Consequently, it is sometimes called emergent materialism or property dualism. In the broad sense, nonreductive materialism holds that everything is physical or at least dependent upon the physical; and in the narrower sense it holds that the mind can have both physical and nonphysical aspects even though it must be instantiated in a physical system like the brain.
While metaphysical materialism entails a materialist theory of mind, one can be a materialist about the mental without believing that everything is physical (e.g., some theologians are nonreductive materialists about the human mind but believe that God is neither physical nor dependent upon the physical; and some philosophers who think that the mind is purely physical also believe in nonphysical abstract objects).
In this chapter, I describe evidence for the view that the human mind is a physical entity, in much the same way in which the human digestive system or the human immune system are physical entities. The first section characterizes this view more fully. The second section explains the evidential relevance of physicalism about the mind to theism. The third section sketches two kinds of evidence that support physicalism about the human mind, while the final section considers an antiphysicalist response to the reasoning of the previous section.
According to physicalism, what we ordinarily take to be a causally undetermined mental action is both caused and determined. But if physicalism is true, important elements of the first-person point of view are mistaken: Andrew Melnyk’s choice to write his paper is not ultimately and irreducibly explained by a purpose, but by the nonpurposive causes of events in his brain. Physicalism implies that at bottom there are not purposive and causal explanations, but simply causal ones, and that there are not free and determined events, but only determined ones. Given these implications, why think that physicalism is true?
In “A Case for Physicalism about the Human Mind,” I tried to assemble positive evidence that physicalism about human mentality is true, while insisting that no aspect of human behavior makes it necessary to adopt any kind of dualism about human mentality. In their reply, Charles Taliaferro and Stuart Goetz fail to engage my positive case for physicalism, and offer no examples of human behavior that can only be explained by some kind of dualism. Instead, they primarily object that my paper overlooks features of human mentality purportedly incompatible with physicalism and accessible only from “the first-person point of view,” such as free choice and reasons for acting. My response focuses on this objection alone.
Vitzthum surveys the materialist philosophical systems of Lucretius, Baron d’Holbach, and Ludwig Buechner, then turns to a discussion of 20th century materialism. Before delving into the mind-brain problem, he outlines the “metascientific” assumptions of materialism, their atheistic implications, and what materialism entails about life and mind. A brief consideration of the ontological status of numbers and moral concepts turns to a discussion of the success of reductionism in contemporary science.
Those who closely study the origin, development, and structure of the universe tend to disbelieve in any spiritual dimension to it. Science has inadvertently discovered that religious pictures of the world are false; when speaking to the same questions, science and religion invariably get different answers. Cosmology has no need for a First Cause since the Big Bang might simply be a transitional phase in an infinitely old universe or, alternatively, there may be no “before” the Big Bang anymore than there is a “north” of the North Pole. Appeals to alleged fine-tuning are presumptuous: physicists extrapolating from the earliest well-understood moment after the Big Bang using the laws of physics alone would erroneously deem our universe inhospitable to life. How, then, can we reliably anticipate the likelihood of life arising in hypothetical universes with different laws? Even supposing that physical constants are in fact “tunable” (which they may not be), constants might take on different values in other universes; and as Carroll puts it, “intelligent observers will only measure the values which obtain in those regions which are consistent with the existence of such observers.” Finally, cosmology betrays unintelligent design: entire classes of fundamental particles exist that would have no impact on life if they had never existed. Evidently, a simple materialist formalism could offer a complete description of the universe.