Philosophy of Mind

4th January 2021

I recently completed an Oxford University short course on Philosophy of Mind. This is an area I have interested in (or maybe I should say tormented by) for a long time.

I would like to write some more on this at some point, but for the moment I have just copied the final essay of the course below. Probably it wont be of interest to anyone, but I feel it might as well go here as anywhere, or nowhere.

Can one reasonably be a dualist in this day and age?

Before attempting to answer this question, it is important to clarify what we are referring to by the term ‘dualism’ and to delineate the scope of what we are wanting dualism to be a reasonable explanation of.  For example, we might construct an argument that makes a reasonable case for dualism as an explanation of those subjective conscious experiences (such as seeing a colour), known as qualia, but that fails to account for the possibility of mental states interacting with and controlling the physical, as is required for mental causation and our apparent capacity for exercising free-will.  Whether we consider the position of the dualist ‘reasonable’ may depend on whether we consider these phenomena real and in need of explanation.

We assume here that qualia are real and so reject forms of eliminativism that conclude otherwise. Further, while we look for reasonable explanations of qualia, we leave aside, initially, questions of mental causation. In this way we allow (though do not necessarily endorse) the theory of epiphenomenalism, which holds that mental phenomena, though real, have no causal agency. This is a significant step as it removes the need to address questions of how the mental might influence the physical and whether physical events can have non-physical causes, a possibility denied if, as is often stated, the universe is ‘causally closed’.

Dualism comes in two flavours; substance dualism, as most famously expounded by Rene Descartes in 1641 and property dualism. Substance dualism suggests that there are two fundamentally distinct substances in the world; the material substance, as explored and to some extent understood by the science of physics and a mind substance, hitherto unknown, other than, it would be argued, through subjective experience.  Property dualism on the other hand holds that there is only one substance; the material substance of physics, of which mental phenomena are a property. We take the dualism of the title question to refer to either of these flavours. 

It might seem from the above that one or other form of dualism must be true.   Under the proposition that qualia exist and as they appear not to be accounted for by our current scientific understanding, they must surely be due to either a new undiscovered mind substance (substance dualism) or a new undiscovered property of material substance (property dualism).  

Contra to this impression however there are philosophies of mind that are classified as neither substance nor property dualism. For example, reductive physicalist theories are generally considered distinct from property dualist theories, even though both propose the existence of only one type of substance: physical matter.

Such distinctions seem to depend on how we define, label and group properties.  Property dualism holds that mental properties are ‘ontologically distinct’ from, or somehow ‘over and above’ physical properties, whereas reductive physicalist theories hold that all properties, including those that account for mental phenomena, are physical.   

The interpretation of the word ‘physical’ seems to be pivotal here. What do we mean by ‘physical’? Physical seems, generally, to be taken to mean ‘as known to science’ or more specifically physics. But physics is an evolving discipline, so ‘as known to physics’ is a time dependent category. If we take the physical to be defined with respect to the current state of physics then reductive physicalism appears to be false, unless we think consciousness can be explained by current physics, in which case we might reasonably ask what combination of currently accepted physical properties (velocity, mass, charge, etc) accounts for my subjective experience of the colour red. If on the other hand we take physics to refer to some ideal future body of knowledge then reductive physicalism might be considered trivially true, since it might be expected physics will expand to include the phenomenon of consciousness in time. This difficulty around the definition of ‘physical’ is expressed in similar terms by Hempel’s dilemma (Hempel 1969) and is a problem in delineating physicalist theories of mind.

Taking the definition of ‘the physical’ as ‘that known to current physics’ as the most reasonable option we suggest the following three propositions.

  1. that the physical domain is defined as that described by today’s physics
  2. that qualia are real
  3. that current physics is unable to explain qualia

These propositions seem to entail property dualism and so, if we consider them reasonable, being a dualist, of one sort or another, must also be reasonable.

So far, we have deliberately made no reference to the need to account for mental causation. Such a position allows epiphenomenalism and coincides with David Chalmers Type-E Dualism, (Chalmers 2002). If we reject epiphenomenalism and require the mental to have causal agency, we must consider how mental events can affect physical events and must allow that such considerations may change our judgement as to whether or not dualism is reasonable.

Considering it desirable to not multiply entities unnecessarily, (and given natural constraints on the scope of this essay), we choose to concentrate on the possibility that mental causation can be accounted for using properties of the material world, i.e. we investigate property dualism. 

The main difficulty with ascribing the mental to properties of physical matter is that we think we know how physical matter works.  Working from the microphysical level we assume an upward causation, from the small to the large (from atoms to molecules to materials etc) thereby achieving, at least in principle, an explanation of the entire universe. Such upward causation seems to leave no room for the physical to be affected by some unknown mental process.  Opposed to this conclusion however is the idea that there may be gaps in this causal chain which are not readily apparent and at which other effects may emerge.

The two most cited candidates for such gaps are the quantum realm or the realm of the complex. The second of these gives rise to the idea of emergentism which holds that new properties arise when objects attain a certain complexity. At and above this complexity threshold the arrow of causation may be reversed, so that the behaviour of the whole can no longer, even in principle, be derived from an understanding of the parts. While it seems, many physicists would dispute the possibility of such emergent properties, other notable physicists offer it some support.  For example, the physicist and cosmologist Paul Davies discusses (Davies 2004) how there are arguments from within physics that leave the way open for downward causation at certain levels of complexity: 

“The numerical results of the previous section may be used to estimate the threshold of complexity beyond which there is no conflict between the causal determinism of the microscopic components and the existence of emergent laws or organizing principles at a higher level.”

The relevant complexity is calculated via a theoretical computability argument and he suggests, within the same article, that:

“… the key molecules for life—nucleic acids and proteins— become biologically efficacious at just about the threshold predicted by the Landauer-Wheeler limit, corresponding to the onset of emergent behaviour”

The thrust of the article is not to prove that emergent properties or downward causation exist, but to loosen fundamental objections to their so doing.

The second candidate for downward causation is the quantum realm.  As is well known and discussed in Chalmers (Chalmers 2002), observation by a conscious observer has long been mooted as a possible cause of ‘wave function collapse’, in which the smoothly evolving wave function, which allows a superposition of multiple states, collapses to a single measured reality.  More recently ideas of ‘de-coherence’ seem to be lessening the need for the conscious observer in this process.  However, it has more recently been suggested that phenomena such as quantum entangled states, do in fact exhibit emergent properties and allow downward causation. In their paper ‘Event ontology in quantum mechanics and downward causation ‘ Gambini and Pullin (2016) conclude;        

“We show that several interpretations of quantum mechanics admit an ontology of objects and events. This ontology reduces the breach between mind and matter”

“Basically, downward causation is present when the disposition of the whole to behave in a certain way cannot be predicted from the dispositions of the parts. The event ontology of quantum mechanics allow us to show that systems in entangled states present emergent new properties and downward causation.”

Reading Davies’ article or, more so, the quantum article cited above, brings to the fore a difficulty with our attempt to establish the reasonableness or otherwise of dualism. In considering subjects such as quantum physics and downward causation we are quickly drawn into highly technical areas of a very specialist nature. If we do not have the specialist knowledge (specialist even within the discipline of physics) to follow and critically evaluate such arguments how shall we proceed? 

We are forced to the somewhat unsatisfactory conclusion that if reasonable and knowledgeable men and women can take particular positions regarding such technical questions, we are beholden to at least allow that holding such opinions is reasonable. It follows that we should be free to consider the possibility of downward causation, emergent properties and property dualism as at least reasonable propositions, even when including mental causation within our ontology.

Beenakker, C. (2007) ‘Hempel’s Dilemma and the Physics of Computation,’ Knowledge in Ferment: Dilemmas in Science, Scholarship and Society (Leiden University Press)

Chalmers, D.  J. (2002) ‘Consciousness and its Place in Nature,’ Published in (D. Chalmers, ed) Philosophy of Mind: Classical and Contemporary Readings (Oxford 2002).

Davies, P. (2004) ‘Emergent biological principles and the computational properties of the universe,’ Complexity. 10. 11-15. 10.1002/cplx.20059.

Gambini, R. and Pullin, J. (2016) ‘Event ontology in quantum mechanics and downward causation,’ International Journal of quantum foundations 2, 89, 2016

Hempel, C. (1969) ‘Reduction: Ontological and Linguistic Facets’, in S. Morgenbesser, et al. (eds.), Essays in Honor of Ernest Nagel, New York: St Martin’s Press.

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