Epiphenomenalism from the Causal Exclusion Problem

I argue for a naturalistic metaphysics leading to the conclusion that epiphenomenalism best fits the data. It is a reductive ontology in which all powerful properties are those existing at the fundamental level posited by physics. It is not reductive about the essence of phenomenal properties; they assuredly exist, but in a way distinct from what third-person scientific data can display.
I begin with physicalism and conclude that all common definitions are deficient in some respect; a working definition is presented. Next, I examine the causal closure of the physical, which forms the basis for accepting epiphenomenalism. Given the truth of causal closure, there is no room for any dualism regarding powerful properties distinct from the bottom level of physics, which concerns fundamental fields and particles. I then discuss the causal exclusion principle and argue against several attempts to preserve genuine mental causation.
Finally, I examine the ontology of properties within the framework of their categorical and dispositional natures. I argue that all properties are categorical in essence. Physics reveals the dispositional subset of these categorical properties. Yet I contend there is one exception existing outside the dispositional domain: qualia. They are purely categorical, existing as “phenomenal aspects,” a unique mode instantiated only by certain organisms. They are ontologically real but causally inert.