Physicalism: some assumptions versus an implication

While physicalism is considered the orthodox position within philosophy of mind, it has by no means been established as irrefutable. One of the major difficulties confronting physicalism is its ability to fully explain the appearance of higher-level causation. The implication of this difficulty is that as long as we lack explanations for causal chains involving chemicals, organisms, social groups and other higher level phenomena in a purely physical language, there is always the possibility of another explanation trumping physicalism. Support for eliminative and reductive forms of physicalism has been in decline since the latter part of the twentieth century, only to be balanced by an increase in support for non-reductive physicalism. In this paper I will discuss the aspiration of non-reductive physicalism to remain a form of physicalism while endorsing the causal independence of non-physical properties. There are two core commitments that have been established as distinguishing physicalism from other metaphysical doctrines such as idealism or dualism. The first is the principle of physical causal closure. This can be taken to mean that any particulars, events, or properties that have causes, have only physical causes. A stronger version states that there is no causal interaction whatsoever between the physical and non-physical domains. A non-physical domain is any domain of phenomena not fully explainable in the terms of the physical sciences, although, mental phenomena are regarded as the most salient example. The second commitment is that everything non-physical supervenes on the physical domain, otherwise known as lack of independent variation. This commitment demands that any change occurring in a non-physical domain must be accompanied by a change in the physical domain. I will argue that if non-reductive physicalism is to sustain claims of independent higher-level causation, then a commitment to the principle of physical causal closure will have to be abandoned. Supervenience, on the other hand, must be retained if non-reductive physicalism is to remain a physicalist doctrine.