In his book Mind and Cosmos, Thomas Nagel suggests neutral monism as a potentially better way of understanding the relation of the mind to the physical world than the traditional alternatives of materialism, idealism and dualism.
However, as Peter Godfrey-Smith pointed out in his review in the London Review of Books, Nagel has in mind here an interpretation of the idea of neutral monism that would:
Explain the appearance of mental life at complex levels of biological organization by means of a general monism according to which the constituents of the universe have properties that explain not only its physical but also its mental character.
The proposal here is that what we encounter as entities and events that appear to be either physical or mental are in fact manifestations of some more basic ontology that includes both types of mechanism.
This turns the proposal into an interesting metaphysics which might be called reductive idealism. Reductivism is associated with the causal closure of physics hypothesis, which is the idea that physics would explain everything if only we had the ability to examine the world at that level of granularity and had the tools available to manage that level of complexity. It is usually labelled reductive materialism, although materialism as such has long been untenable as an ontology.
Nagel can propose this alternative interpretation because reductivism is not the same thing as reductionism. Following Nagel’s usage, reductive theories seek to explain complex wholes in terms of their simplest and most primitive components while reductionist theories seek to explain cultural and social events as physical and biological events. Explaining evolutionary biology in terms of physics and chemistry is reductive; explaining language, trade and warfare in terms of evolutionary biology is reductionist. If explanations are viewed as components of a hierarchy at different scales, reductive theories are vertical integrations and reductionist theories are horizontal integrations.
In this framework, reductive materialism is both reductive and reductionist, whereas reductive idealism is just reductive.
The most significant problem with Nagel’s thesis is that it is highly speculative. The difficulties that materialist theories have in explaining consciousness, cognition and value are real, but solutions have to be argued on their merits.
I agree that neutral monism is the most persuasive alternative to materialism and idealism or any kind of dualism but I think there is a better interpretation of what this implies. In his review, Godfrey-Smith continues:
He [Nagel] thinks we have a clear idea of what the mental and physical are, that we can see neither can be reduced to the other, and that the only way to make sense of the situation is to say that all of nature, at bottom, contains a bit of both. A different and to my mind more promising version of the view has a more critical flavour. It holds that standard ways of thinking about the mind-body problem are dependent on crude conceptions of both the mental and the physical. We think we have a clear and definite idea of what a ‘purely physical’ or ‘purely mental’ process is like, but our grasp of both is so poor that we do a bad job of thinking about how they might be related, and see a gulf that isn’t really there. Nature gives rise to what appear to us as ‘physical’ processes and ‘mental’ processes, but both arise from something that fits into neither of these crude categories.
Neutral monism means neither rather than both. It means seeing without the mind-body filter at all.
What we then observe are patterns of events at different scales and evolving according to different principles. Some systems evolve organically, some mechanically, some statistically. Some systems are self-organizing, some self-sustaining, others are just loosely interacting through adjustment and accommodation. With some systems we posit that the events we observe are the outward expression of an interior life, with others we don’t, and we shift systems between these classifications depending on how successful the explanations are.
All systems are built from physical and chemical components, so that in itself doesn’t explain why some systems are organic and some inorganic. But it does suggest that there is nothing in the pattern of events at the sub-atomic scale that constrains macro-scale systems to being inorganic. Both organic and inorganic macro-scale systems can be built from the same inorganic sub-atomic components.
This shift comes from treating organic and inorganic as patterns of system evolution rather than compositionally. If we do the same thing with consciousness, and think of it as a pattern in the evolution of events, a fashion in which some organic systems evolve, then we will see that there is no a priori reason to suppose that the pattern of events characteristic of conscious organic being is incompatible with the pattern of events characteristic of the evolution of inorganic, non-conscious, sub-atomic systems.
Looking at things in this way requires a shift in perspective which has two components. The first is to find the right relationship between the synchronic, the structure at a moment in time, and the diachronic, the evolution of the structure through time. The second is the way in which macro-scale systems are partitioned and the consequent encapsulation of micro-scale processes.
We need to pay more attention to the diachronic.
Atomic systems aren’t being created from sub-atomic components on a day-to-day basis, they were formed before the earth and will persist, more than likely, until its end.
The components of biological systems are physical and chemical. But those components aren’t organised into biological systems in the moment. Biology doesn’t emerge in that sense from physics and chemistry. Biological systems come from biological systems and that continuity has been maintained unbroken for millions, maybe billions, of years.
Similarly, cultural events come from cultural events, and have done for at least 40,000 years, probably much longer. If our cultural inheritance were lost, we would have to start again from the beginning.
And the same applies to our own lives; our inner life is not constituted moment by moment, or even as a chain of experiences, but is a continuous flow.
We need to pay more attention to partitioning.
Stable and resilient macro-scale systems are created by the partitioning and consequent encapsulation of the micro-scale. What happens is that at each scale the micro-scale is divided up, so that rather than being a single system, the micro-scale is composed of sub-systems. As a result, the evolution of the system is determined at the macro-scale and constrained by the micro-scale.
The relationship between systems and sub-systems becomes one of constraints rather than causes.
In this model, atoms and molecules are, relatively speaking, macro-scale systems. The biosphere is partitioned into cells, organisms, and species. Conscious organisms become individual beings and human beings become introspectively aware of their own individuality and acquire a cultural inheritance and, in the process of cultural development and acquisition, systematic patterns of thought and imagination are constructed and transmitted.
Nagel, T. (2012). Mind & Cosmos. Oxford: Oxford University Press.