The claim that reality’s fundamental building blocks are conscious can seem to challenge what physics tells us the world is like. It’s no surprise then to find prominent physicists arguing that panpsychism is incompatible with physics, and therefore false. But that would be to misunderstand panpsychism: It’s not a competing scientific theory, but a philosophical interpretation of the claims of physics, argues Philip Goff.

Sean Carroll will debate this issue with Philip Goff and Keith Frankish live on the 'Mind Chat', YouTube channel 11th November, 2pm UK time: https://www.youtube.com/c/MindChat

Panpsychism is the view that consciousness is a fundamental and ubiquitous feature of the physical world. It is the view that the basic building blocks of the physical universe – perhaps fundamental particles – have incredibly simple forms of experience, and that the very sophisticated experience of the human or animal brain is rooted in, derived from, more rudimentary forms of experience at the level of basic physics. Panpsychism has received a lot of attention of late. The world of academic philosophy has been rocked by the conversion of one of the most influential materialists of the last thirty years, Michael Tye, to a form of panpsychism (panprotopsychism) in his latest book. And the main annual UK philosophy conference held a plenary panel on panpsychism this year for the first time in its history.

Much of the attention has been critical, which is as it should be when it comes to matters on which there is little consensus. Among the recent critics are two leading theoretical physicists: Sabine Hossenfelder and Sean Carroll, who argue that panpsychism is incompatible with what fundamental physics tells us about the building blocks of the universe. However, these objections rely on a misunderstanding of what panpsychism is. Panpsychism is not a scientific theory in competition with physics, and therefore not incompatible with it. It’s rather a philosophical interpretation of the claims of physics.

Physicists against panpsychism

Hossenfelder has argued that there is a clash between panpsychism and the standard model of particle physics, our best physical theory of the 25 known fundamental particles. The standard model characterises particles in terms of their physical properties – such as mass, spin, and charge – and makes precise predictions on that basis. Hossenfelder’s thought is that if, in addition to their physical properties, particles also had non-physical consciousness properties, these latter properties would presumably have an impact on the behaviour of the particles, resulting in predictions different from those of the standard model (as the standard model makes its predictions solely on the basis of the particles’ physical properties). The predictions of the standard model are very well-confirmed, and so, according to Hossenfelder, we ought to reject panpsychism.

Hossenfelder has argued that there is a clash between panpsychism and the standard model of particle physics, our best physical theory of the 25 known fundamental particles.

In a recent collection of articles responding to my book Galileo’s Error, Sean Carroll makes a similar argument, although rooted in the clash between panpsychism and the Core Theory: the standard model combined with the weak limit of general relativity. We don’t yet have a complete physical theory of the universe, not least because our best theory of big things – general relativity – clashes with our best theory of little things – quantum mechanics. However, these clashes only emerge in context of high energy or high gravitation, conditions that would be met, for example, if you stepped into a black hole. In terms of how the matter of our bodies and brain behaves in terrestrial conditions, the Core Theory is able to bring together the standard model and general relativity.

Hossenfelder simply misunderstands panpsychism. She interprets panpsychism as a form of dualism. But panpsychists are not dualists.

From that point onwards, the argument is similar to Hossenfelder’s. Carroll is sceptical of the idea that consciousness is a fundamental feature of matter. If it were, then we’d expect to see its effects on the matter in our bodies and brains, resulting in predictions that differ from those of the Core Theory, the predictions of the latter being based on the physical properties of matter rather than panpsychist consciousness properties. Given the evidential support for the Core Theory, the argument goes, we should reject any theory that clashes with it, including panpsychism.

Panpsychism as an interpretation of physics

How should the panpsychist respond to these challenges? Hossenfelder simply misunderstands panpsychism. She interprets panpsychism as a form of dualism: there are the physical properties of the particles (mass, spin, charge) and then, in addition, certain non-physical consciousness properties. But panpsychists are not dualists. According to panpsychism, an electron doesn’t have two kinds of property: physical and non-physical. Rather, it’s physical properties (mass, spin, charge) are forms of consciousness. Consciousness is the ultimate nature of the physical.

This point leads to a lot of confusion, and so is worth dwelling on. How can consciousness be the nature of the physical? Doesn’t physics tell us the nature of the physical? Well, what physics gives us is a purely mathematical description of reality. On one dominant view in theoretical physics, what we find at the fundamental level is the wave function, a very high dimensional space that physicists characterise in purely mathematical terms. Now, there are a couple of ways one might respond to the fact that physics is purely mathematical. One option is to follow the physicist Max Tegmark in concluding that reality itself, at its base, is purely mathematical. Another option, the one taken by the panpsychist, is to hold that there is something that underlies this mathematical structure. Stephen Hawking famously said that physics doesn’t tell what ‘breathes fire into the equations’ and ‘makes a universe for them to describe.’ According to panpsychism, it’s consciousness that breathes fire into the equations.

In what sense does consciousness underlie the mathematical structures of physics? According to panpsychism, all that exists at the fundamental level of reality are networks of conscious entities. However, those conscious entities behave in certain predictable ways, in virtue of the kinds of experiences they have, and that behaviour can be modelled mathematically. The result is physics. Physics describes the behaviour of fundamental conscious entities, but does so in way that abstracts from their experiential nature, focusing only on the abstract patterns they realise through their interactions.

Panpsychism is not a competitor to physics. As a philosophical interpretation of physics, it is rather in competition with other philosophical interpretations of physics.

That sounds a bit weird. If you’re doing physics, it doesn’t feel like you’re studying networks of conscious entities. But that’s because when you’re doing physics you’re just interested in mathematical structure, not in what, if anything, underlies that mathematical structure. The latter question is one for philosophers.

Properly understood, then, there is no clash between the standard model and panpsychism. Panpsychism is not a rival scientific hypothesis to the standard model, it is rather a philosophical interpretation of the standard model, according to which the standard model records the mathematical structures realised by fundamental conscious entities.

There is also no clash with the Core Theory, for the same reason. To be fair to Carroll, however, he does consider an interpretation of panpsychism he calls ‘passive mentalism’, the view that ‘there exist purely mental aspects of the basic ontology of the world that have no effect at all on physical dynamics.’ He rightly rejects passive mentalism as an implausible hypothesis:

"Crying at a funeral is behavior, as is asking someone to marry you, as is arguing about consciousness. No compelling account of consciousness can attribute a central explanatory role to metaphysical ingredients that have no influence on these kinds of behaviors."

But passive mentalism is not panpsychism either. To repeat: all that exists at the fundamental level, according to panpsychism, are conscious entities. And those entities are doing what they do because of the kinds of conscious experiences they have. When, ignorant of the experiential nature of the properties of particles, we refer to them in terms of the mathematical structures they realise through their behaviour, we call them ‘mass’, ‘spin’ and ‘charge.’  But it’s not as though there are on the one hand the physical properties of particles, and their consciousness properties on the other (again, this would be dualism rather than panpsychism). There are just fundamental conscious entities, and physics reports the mathematical patterns they form through their interactions.

We know that consciousness does exist in our world, and therefore, we do not live in a Pythagorean world. This leaves us with a choice between panpsychism and dualism.

Panpsychism is not a competitor to physics. As a philosophical interpretation of physics, it is rather in competition with other philosophical interpretations of physics. But why on earth would we take the panpsychism interpretation of physics seriously, when Tegmark’s interpretation of there being only mathematical structure seems more parsimonious?

Essentially, when it comes to understanding the relationship between our mathematical models of the world and our experiences of consciousness, I believe we have to decide between three options:

1. Pythagoreanism: Reality is in itself a purely mathematical structure
2. Dualism: Physical reality is pure mathematical structure, but there is also non-physical consciousness.
3. Panpsychism: There are only conscious entities, and some of them realise the mathematical structures identified by physical science.

In my humble opinion, there are powerful philosophical arguments which demonstrate that a Pythagorean world would be one that lacked consciousness, as the qualities we are acquainted with in our conscious experience (colours, sounds, smells, tastes) cannot be captured in the purely quantitative language of mathematics. We know that consciousness does exist in our world, and therefore, we do not live in a Pythagorean world. This leaves us with a choice between panpsychism and dualism. As philosophers and scientists, we try to find the simplest theory able to account for the data. Panpsychism is simpler than dualism, and is therefore the theory to be preferred.

That was a very quick argument, and each step in it involves contentious assumptions that we continue to debate. It would be nice if we could do an experiment to settle the issue, but these are not the kinds of questions you can answer with experiments. For these questions, you need philosophy.