Jaegwon Kim tells us it all started with two papers published a year apart in the late fifties: “The ‘Mental’ and the ‘Physical'” by Herbert Feigl in 1958 and “Sensations and Brain Processes ” by J. J. C. Smart the following year. Both of these men brought about a qualitative change in our approach to the study of the brain and its interactions with the physical substrate. Each of them proposed in independent studies an approach to the nature of mind that has come to be called the mind-body identity theory, central-state materialism, the brain state theory, or type physicalism. That the identity theory in itself would lose traction and other theories would come to the fore, the actual underlying structure of the debates would continue to be set by the framework they originally put in place. As Kim suggests:
What I have in mind is the fact that the brain state theory helped set the basic parameters and constraints for the debates that were to come – a set of broadly physicalist assumptions and aspirations that still guide and constrain our thinking today.1
This extreme form of reductionist Physicalism was questioned by the multiple realizability argument of Hilary Putnum and the anomalous argument by Donald Davidson. At the heart of Putnum’s argument as the notion of functionalism, that mental kinds and properties are functional kinds at a higher level of abstraction than physicochemical or biological kinds. Davidson on the other hand offered the notion of anomalous monism that the mental domain, on account of its essential anomalousness and normativity , cannot be the object of serious scientific investigation, placing the mental on a wholly different plane from the physical. At first it seemed to many of the scientists of the era that these two approaches, each in its own distinctive way, made it possible for “us to shed the restrictive constraints of monolithic reductionism without losing our credentials as physicalists” (4). Yet, as it turned out this, too, did not last.
Ultimately Davidson’s theory of anomalous monism failed because of what it could not say about the Mind-Body debate: it could not offer a solution to why mental and physical events relate at all. His thesis was based solely on the descriptive theory of mental and physical kinds in which there are no events that have only mental properties (descriptions), although there may be, and presumably are, events with physical properties (descriptions) only (4). The point being here as Kim suggests “we want our mind-body theories to tell us more, a positive story about how mental properties and physical properties are related, and hopefully also explain why they are so related. We don’t get such a story from anomalous monism (5). Davidson’s theory could not supply this.
It was because many scientists and philosophers of mind questioned Davidson’s theory that he modified it to reveal a new a new concept “supervenience“, which is an ontological relation that is used to describe cases where (roughly speaking) the lower-level properties of a system determine its higher level properties. What many physicalists of the ear found congenial in this concept was the notion that an asymmetric dependence of the mental on the physical is clearly implied , if not stated outright (6).
On the other side were the functionalists (Putnum), who, by and large, were not metaphysicians, and few of them were self-consciously concerned about just what their position entailed about the mind-body problem (6). For the functionalists the key term for the relation between mental and physical events was another concept, “realization” (or sometimes “implementation ,” “execution,” etc.): mental properties are “realized” or “implemented ” by (or in) physical properties, though neither identical nor reducible to them (7).
Because the philosophical presuppositions underpinning both of these theories was embraced by most physicalists by the mid-70’s it came to be known as “nonreductive physicalism” (or “nonreductive materialism ” ), and has been, and still is, the most influential metaphysical position, not only on the mind -body problem but more generally on the relationship between higher-level properties and underlying lower-level properties in all areas (8).* With this new non-reductive approach to Physicalism an old idea began to emerge: the notion of emergentism. As Kim relates it:
In the heyday of positivism and “unity of science , ” emergentism used to be relegated to the heap of unsavory pseudoscientific doctrines , not quite as disreputable as, say, neo-vitalism with its entelechies and elan vital , but nearly as obscure and incoherent. With the demise of reductive physicalism, emergentism has been showing strong signs of a comeback. (8)
In summary three ideas have been, and still are, prominent in discussions of the mind-body problem since the demise of the reductive brain-state theory: the idea that the mental “supervenes ” on the physical, the idea that the mental is “realized” by the physical, and the idea that the mental is “emergent” from the physical.
In my next post I’ll return to the work of Thomas Nagel who has incorporated a form of emergentism into his thought.
1. Jaegwon Kim. Mind in a Physical World: An Essay on the Mind-Body Problem (Providence, 1997)
*(note: this text was written back in 97 so there have been other changes since, which I’ll need to incorporate at some future date)