Is there nothing over and above the physical?|
Physicalism roughly states that "everything is physical". It is often combined with the reductive belief that everything can be explained by reference to its physical basis. However, nowadays the term is usually introduced via the supervenience relation which may also allow for a non-reductive version of physicalism (see e.g. Stoljar, 2001).
Obviously, the chief target of physicalism is the mental, i.e. the notion that the mental is "fundamental" or "primitive". To put it metaphorically, it is about the question if God had only to introduce the physical entities and the "mental" would follow from them or if the "mental" was an independent item on his "shopping list" when he set up this place.
In the following I will mainly annotate and excerpt a paper by Crane and Mellor (1990) in which they argue that "physicalism lacks a clear and credible definition, and that in no non-vacuous interpretation it is true" (p.185). According to them neither any reference to reduction, causation or laws can support the alleged ontological authority of the physical (as opposed to the mental). However, note that this is not taken as evidence for a dualistic picture.
Physicalism and materialism
Physicalism may be construed as a descendant of "materialism", say, the notion that there were only atoms in the void. However, there seems to be a significant difference. The old materialism was a metaphysical doctrine, i.e. an attempt to limit physics a priori. "Matter" was required to be solid, inert, conserved etc. But in the meantime physics has discovered that matter is lacking all of this properties! Therefore, "materialism's modern descendants have - understandably - lost their metaphysical nerve" (Crane and Mellor 1990, p.186). This holds especially for "physicalism" in its original version since this term was coined by Otto Neurath and was part of the repertoire of logical empiricism. Nothing could have been more foreign to members of the Vienna circle than setting up a new metaphysical doctrine! According to them the role of philosophy was not to set up any propositions (which was the job of the positive sciences) but rather to explain their meaning by linguistic (i.e. logical) analysis. Their physicalism was conceived as the claim that the language of physics is suited best to represent the knowledge in an inter-subjective and observation based way. This view was silent on many traditional philosophical questions or actually they were declared "pseudo-problems" (Carnap). The mind-body problem was conceived as one of them.
The heyday of logical empiricism is long ago and e.g. Carnap was among the first to recognize important shortcomings of the empirical meaning criteria etc. Somehow the old ontological questions came back on the agenda and the mind-body problem is no more viewed as a "pseudo-problem". However, current physicalism is "no longer trying to limit the matter of physics a priori" but claims that the empirical world "contains just what a true complete physical science would say it contains" (Crane and Mellor 1990, p.186). But how can such an ontological authority of the "physical" (as opposed to the mental) be justified? Crane and Mellor make a very conclusive case that this is indeed not possible.
The case against physicalism
Crane and Mellor (1990) argue that "physicalism lacks a clear and credible definition, and that in no non-vacuous interpretation it is true" (p.185). First they turn to the question what "physical" is supposed to mean, i.e. why for example psychology is not a physical science. As argued above, the claim that "thinking" is no respectable physical property can not be based on a metaphysical doctrine ala old-style materialism. But what other reason do we have to deny that psychology adds "in its own terms, as physics does, to our inventory of what there is?" (p.186).
Crane and Mellor suggest that this distinction may be based on the requirement that true physical sciences (chemistry, biology etc.) can be reduced to physics. First one has to acknowledge that "reduction" can only mean "reduction in principle" (RIP). Even it adherents do not propose to do it in practice. However, what then is this principle? It can not be physicalism since RIP "is supposed to tell us where the bounds of the physical lie" (p.188). Further more one runs into "Hempel's dilemma", i.e. the question to what physics the reduction is supposed to be applied. The present physics can not be meant. It is totally unreasonable to regard current physics as finished or to qualify future developments of physics as unphysical. However, if one means an unspecified future physics the answer to the question "what is physical" has to wait for the advent of this future theory (which should take infinite long). And perhaps this future physics does even include what is at present conceived as mental entities!
The reduction mentioned above was a conceptual issue. The common intuition behind physicalism in general and reduction in particular is the "idea that there is really no more to things than the smallest particles they are made up of" (p.189). This thesis is called "micro reduction" (MR). Here Crane and Mellor make the following insightful remark:
"Now the study of the smallest entities is indeed traditionally called "physics": departments of physics have a long established custom cornered that particular market. [...] The fact that physics by mere convention includes the study of the very small does indeed trivially entails that everything extended in space either is physical or has some physical parts [...] But for physicalism so defined to be non-vacuous, one must also take these smallest things to be all there is. But what reason is there to think this?" (p.189)Crane and Mellor are the first to admit that "facts about parts often explain facts about wholes" (p.190), i.e. that MR is often a very good working hypothesis about explanation. But for example entanglement in orthodox quantum mechanics points to its failure even in micro-physics! Further more they quote Mach's principle for a piece of "macro-reduction" in physics. Crane and Mellor notice that orthodox quantum mechanics or Mach's principle are controversial - future physics might abandon them. However they illustrate that MR is not entailed by modern microphysics.
But Crane and Mellor move a step further. Even if micro-reduction would (as an explanatory principle) always hold, it would not support it as an ontological thesis. Just like atoms happily co-exist with their subatomic parts.
"The existence of animals and people, with their psychological and social properties and relations, cannot be denied just by crediting them with parts small enough to matter to microphysics.According to Crane and Mellor mechanics or micro-physics are no more universal than any other science, they are "merely the special sciences of motion and of the very small" (p.191).
Given that reduction or micro-reduction do not allow for any convincing definition of the physical and its alleged ontological authority Crane and Mellor move to the question of causation. What, they ask, if the "physical" is just the "causal". The relation to the mind-body problem is clear: it is often framed as the question how mental states can have effects in the physical world.
"It is indeed an old thought that mental causation is hard to make sense of, and especially causation linking the mental to the non-mental, because they seem to be so different. But why should that impress anyone who has learned from Hume that causation never "makes sense": that it is always a matter of fact, not of reason? Nothing in either Humean or other modern analysis of causation forces causes to be like their effects; nor does anything in them stop causes and effects being mental."(p.192)For the details of the argument which involves also the intentionality issue we refer the reader to the Crane-Mellor article (pp. 192-196). A provoking discussion of causality is given in Norton (2003). Norton argues that a scientifically informed metaphysics should rather abandon "causality" as a fundamental concept. He fully acknowledges its practical importance but views it as a derived concept only. An apparent failure of determinism (and causality) in classical physics (i.e. the prime example for a determinstic theory) is discussed here.
Finally Crane and Mellor investigate the claim that the dividing line between the physical and the mental is given by "laws". Some try to rest the ontological authority of the physical sciences on the laws they discover while strictly speaking there are no psychological or psychophysical laws (see e.g. Davidson 1970). However, do we have any reason to deny that "all men are mortal" is a strict psychophysical law? In fact there are many law-like regulations which relate mental sensations (pain, taste, smell etc.) to non mental features. In fact, whole industries depend on these "laws":
"Think of the laws which must underlie the reliable production and use of anaesthetics, scents, narcotics, sweeteners, coloured paints and lights, loudspeakers, and soft cushions. And if Newton's law of motion suffice to add masses and forces to our physical ontology, these laws must suffice to add to it the kinds of sensations that feature in them."(p.198)
The bottom line of Crane and Mellor is not a revival of dualism. In fact they take their argument to support the claim that
"there is no divide between the mental and the non-mental sufficient even to set physicalism up as a serious question, let alone as a serious answer to it. Physicalism is the wrong answer to an essentially trivial question. [...]
I take Crane and Mellor to support the view that we have no compelling reasons to refute free will based on physicalism.
Replies to Crane and Mellor
Philosophy would not be philosophy if the above thesis (as any other) would not be fiercly disputed. The main point of Crane and Mellor is that given the fate of old-style materialsm, physicalists should not make a priori claims about the possible content of any future science. But if physicalism is based on an unspecified future science the doctirne is actually empty. However, some authors do not buy the premise of this argument and base their physicalism on the a priori requirement that physical predicates are not mental, i.e. intentional and phenomenal (see e.g. Loewer 2001 and reference therein). An other tendency in the literature on physicalism appears to be a watering down of the concept. Loewer (2001, p.8ff) gives the following list of unwarranted fears of physicalism:
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