Can Biology Be Reduced To Physics?
18 min read

Can Biology Be Reduced To Physics?

"Physics is the most fundamental and all-inclusive of the sciences." Or is it?


Since the dawn of SubAnima, the question of what makes biology different from physics has always been bouncing around in my head somewhere.

In the first blog post I made (August 2021), I suggested that biology was simply more complex than physics meaning that laws (if they indeed existed) would be much harder to come by. Nonetheless, there are still regularities that exist that repeat all the way through the tree of life, so it's not just pure randomness.

In the first video I uploaded to the channel (December 2021), I suggested that biology and physics both had plenty of mathematical structures upholding them both, but that biology lacked universal laws. That's what made it different.

I still stand by everything I said in those pieces, but now that I've read a bit more I can make these ideas a little more precise.

The most important thing I read from then until now was undoubtedly Robert Rosen's Life Itself which I came across while working through Yogi Jaeger's lecture series Beyond Networks: The Evolution of Living Systems.

In his book, Rosen shows that not only has biology not discovered any laws, but that it never will. While everything in physics can be thought of as a mechanism, the organism lies beyond this category.

The consequences of this realisation are vast and I'm planning to go deeper into Rosen's mathematical argument in the next video. But for this one, I just wanted to give a brief outline of the anti-reductionist position and highlight why physics can't explain everything.

Also important here is the perspectival realist stance which is quite different to the standard realism/anti-realism dichotomy. A huge influence on my thinking has been Michela Massimi's book Perspectival Realism which I read on my post-undergrad vacation in Crete (August 2022). I have no regrets.

Further Reading

The standard reductionist position of "biology is just applied chemistry which is just applied physics" is VERY common so I'm sure it needs no introduction. That said, it may be useful to have few key landmarks on what this position looks like.

For that we can look to Feynman:

The Feynman Lectures on Physics Vol. I Ch. 3: The Relation of Physics to Other Sciences

Or Sabine Hossenfelder:


Purity by XKCD / CC BY-NC 2.5

Or Ernest Rutherford's mythical statement that he probably never said:

All science is either physics or stamp collecting.

Ok that's enough of that. What about the other side?

If you are a die hard physicist who cannot possibly fathom that physics may have its limitations and that it's not the only way of generating knowledge out there, I would suggest Lee Smolin's book Time Reborn or this interview. Hopefully that opens your mind a little bit, and it's from a physicist no less so you don't have to take it from a lowly biologist.

If you are willing to hear the anti-reductionist stance but are not yet convinced, I would suggest Denis Walsh's book Organisms, Agency and Evolution which is the backbone of this series of videos as I've mentioned before. There's also Philip Anderson's classic More is different which is still being commented on.

If you loved the video are amazed at how biological organisms break the Newtonian paradigm and want more details then the next steps would be to read the following:

1. Life Itself by Robert Rosen (1991)

Life Itself | Columbia University Press
Why are living things alive? As a theoretical biologist, Robert Rosen saw this as the most fundamental of all questions-and yet it had never been answered sa... | CUP

2. Perspectival Realism by Michela Massimi (2022)

Perspectival Realism
What does it mean to be a realist about science if one takes seriously the view that scientific knowledge is always perspectival, namely historically and culturally situated? In Perspectival Realism, Michela Massimi explores how scientific knowledge grows and evolves thanks to a plurality of epistem…

3. Re-Engineering Philosophy for Limited Beings by Bill Wimsatt (2007)

Re-Engineering Philosophy for Limited Beings: Piecewise Approximations to Reality on JSTOR
Analytic philosophers once pantomimed physics: they tried to understand the world by breaking it down into the smallest possible bits. Thinkers from the Darwini...

All three of those are hard reads and not for the faint-hearted.

If you want a mid-way stepping stone from my video to those trickier books, there are Yogi Jaeger's lectures:

And also a 3-part interview Yogi did with Jannie Hofmeyr who is doing some important work modernising Rosen's ideas:

And here's one of Jannie's papers taking concepts from Rosen and John von Neumann among others.


Physics is the most fundamental and all-inclusive of the sciences … everything that living things do can be understood in terms of the jigglings and wigglings of atoms.

… is a quote from Richard Feynman in the third lecture in his famous series.

The Feynman Lectures on Physics, Volume I, Chapter 3: The Relation of Physics to Other Sciences / Richard Feynman
The Feynman Lectures on Physics, Volume I, Chapter 3: The Relation of Physics to Other Sciences / Richard Feynman

This reductionist point of view is pretty common today and we can see it in everything from XKCD comics to Sabine Hossenfelder's new book Existential Physics.

Purity by XKCD / CC BY-NC 2.5
Existential Physics / Sabine Hossenfelder

If we could just reexpress organisms, economies and social interactions at the atomic level and apply the laws of physics with a big enough computer, we’d know everything that happens at the higher levels. And in that sense, all the interesting stuff in the universe only really happens at the bottom and we can see everything from down there.

At least, that’s what the physicists tell us.

And unfortunately for them, they’re wrong. The way we study complex systems, like those in biology, simply can’t be reduced to physics.

I know that sounds pretty radical, but hear me out and I’ll explain.

Life Itself (p. xvii) / Robert Rosen

In 1687, Isaac Newton published his Principia Mathematica which would go on to lay the foundations of modern physics. The picture we get of matter from Newton is that it doesn't do anything by itself. That's his first law. If it does happen to move in a particular way, then we know that it must be under the influence of some kind of external force.

Newton’s laws of motion - Wikipedia

But when we look at the biological world, matter seems to move by itself all the time. In this beautiful film of the development of the Alpine Newt, Jan van Ijken shows us just how 'non-Newtonian' biology appears: cells fold in on themselves, limbs seem to emerge out of nowhere, and atoms stop bumping around randomly and start swimming together as one little tadpole.

Becoming - Jan van IJken
BECOMING is a short film about the miraculous genesis of animal life. In great microscopic detail, we see the ‘making of’ a salamander in its transparant egg from fertilization to hatching. The first stages of embryonic development are roughly the same for all animals, including humans. In the film,…

As Denis Walsh puts it more poetically:

If Newton’s laws lay down the rules by which matter conducts itself, organisms flout them flagrantly.
Organisms, Agency and Evolution (p. 9) / Denis Walsh

Of course, I'm not saying that there are any new forces involved in the development of living systems, just that we might need to take a different perspective compared to the Newtonian paradigm.

I would suggest reading this whole chapter (at least) to get a better picture of why the current methods of physics are limited. Time Reborn, Chapter 4: Doing Physics in a Box (p.44) / Lee Smolin

One different idea we can use is the concept of top-down causation. Instead of saying that the jigglings of atoms alone cause the tadpole to move (which is the standard bottom-up perspective), we also need to look at the reverse direction: the atoms are only moving in the way that they are because they happen to be in a tadpole.

Organisms, Agency and Evolution (p. 219) / Denis Walsh

This isn't even that radical. The atoms in this GIF that I keep showing are moving in the way that they are because they are bounded by the box. If the box were a different shape, or missing one of its sides, they would behave differently. This is very simple top-down causation.

Diffusion simulator pretty cool! (PhET Interactive Simulations / University of Colorado Boulder)
Green, S., & Batterman, R. W. (2021). Making sense of top-down causation: universality and functional equivalence in physics and biology. In: Voosholz, J., & Gabriel, M. (2021). Top-Down Causation and Emergence. Springer Nature. Chapter 2, p. 42.

At the scale of atoms alone, we can't see anything really. A warm cup of tea at 37 would look oddly similar to this little newt. From the perspective of molecular physics, the organism disappears entirely.

Putting the organism back into biology - Dialectical Systems
Biology studies organisms. This seems to be a truism. But is this assumption really correct? Some scientists and philosophers hold that it is not. Developmental biologist Brian Goodwin, for example, states: “Organisms have disappeared as fundamental entities, as basic unities, from contemporary bi…

Sure, if we wanted to build a giant supercomputer to simulate features of the biological world at the level of atoms, we might be able to make some predictions about where collections of atoms would end up.

But we wouldn't be able to understand much about biology at all.

Particularly because as systems get bigger, they just happen to have more properties. There are simply more things to say about me than there are about a hydrogen atom. Not only that, but the things you say about me (the colour of my hair, the number of languages I speak, the music I like to play on guitar etc.) cannot be said about the hydrogen atom. More really is different. And on that note, here's one of my favourite excerpts - the final sentence of Philip Anderson's classic More is different (1972).

Take this example, stolen from one of my university lecturers Kristian Camilleri. Say we wanted to understand what caused WWI. If we start our explanation with "So you see there were a bunch of atoms over here, that assembled themselves into a 3D structure we call a bullet," we're not going to get very far.

We clearly need higher level historical explanations like: imperialism, nationalism, the system of alliances and so on. This happens to be the right perspective for generating knowledge in this case. And it can't be reduced to physics without making our explanations meaningless.

A slide from a lecture titled Naturalism, Reduction and Emergence in the University of Melbourne course God and the Natural Sciences / Kristian Camilleri

In the same way, the self-organising characteristics of biology can't be reduced to physics without our view of the organism becoming so diluted that it hardly makes much sense.

Because of the limitations of any one scientific perspective, Michela Massimi calls for a multi-perspectival approach to generating knowledge.

Perspectival Realism (p. 10) / Michela Massimi

We are like blind men touching an elephant and no single perspective of ours will ever be able to give us a complete picture of the universe. Not even physics. We need all of the sciences working together, drawing from one another to put together a full picture.

Perspectival Realism (p. 9) / Michela Massimi
Not only is truth inherently perspectival (we are stuck assessing things from a particular epistemic standpoint, not some 'God's-eye-perspective' from nowhere) but for knowledge claims to be valuable, we need MULTIPLE perspectives to assess them. When a claim holds up from the point of view of many different perspectives, then we can realise that it is getting at something that is true. Massimi's philosophy is a beautiful blend of pluralism and realism. I think it is quite possible the best work in the philosophy of science since Kuhn and Popper. Simply amazing. Massimi, M. (2018). Four kinds of perspectival truth. Philosophy and Phenomenological Research, 96(2), 342-359.

Computer simulations of biochemistry and mathematical models of the physics of organisms certainly are insightful when kept in the right domain. But we should be cautious of thinking that we can construct a model of the whole organism with them.

See 33:05 of this interview on the problems of simulating the whole organism. No doubt we have simulations/models of some of the organism, but Rosen's argument in Life Itself highlights that it is impossible to come up with a largest model for the organism. Jannie and Yogi draw a link between this style of incompleteness argument and Gödel's famous incompleteness theorem.

Because, it's not just a knowledge problem that stops us from using computers and physics to explain everything in biology. Organisms also break down the traditional methods of computing and mathematical modelling that we have today.

The modern computer as it exists today was first conceived by Alan Turing, who initially described them as "universal computing machines." Today we call them universal Turing machines after him and everything that your phone or computer can do, can also be done by a universal Turing machine, so they serve as a catch-all way of understanding computation.

Turing, A. M. (1936). On computable numbers, with an application to the Entscheidungsproblem. J. of Math, 58(345-363), 5 / Link

The structure of a universal Turing machine is pretty simple, it takes its input on a tape full of 1s and 0s, its hardware is a machine head that can slide along the tape and rewrite the numbers on it, and its software is the algorithm that tells the head what to do.

Universal Turing machine - Wikipedia

This picture maps onto physics quite well where the laws seem to be static over time. So we can reasonably call them the 'software' of the particular system we are studying.

But if we try to map this picture onto the organism we run into trouble. Because the quote unquote 'software' of organisms changes over time. For instance, the way an embryo behaves is very different to how an adult behaves.

Not only that, but the way an embryo changes to develop into an adult is somehow self-derived. So it's not a normal Turing machine, but more like one that builds itself.

One of the founders of computing, John von Neumann actually designed a theoretical machine that could construct itself known as a 'universal constructor.' But up until today, no-one has managed to build one.

Los Alamos National Laboratory / Unless otherwise indicated, this information has been authored by an employee or employees of the Los Alamos National Security, LLC (LANS), operator of the Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396 with the U.S. Department of Energy. The U.S. Government has rights to use, reproduce, and distribute this information. The public may copy and use this information without charge, provided that this Notice and any statement of authorship are reproduced on all copies. Neither the Government nor LANS makes any warranty, express or implied, or assumes any liability or responsibility for the use of this information.
Von Neumann universal constructor - Wikipedia

The closest we've gotten are 3D printers that can print most of their own parts like this one called RepRap. The problem is that you still need humans like these guys to put the parts together. I'm sure I don't have to tell you but your parents didn't have to arrange your internal organs while you were growing in the womb, you managed to work that out all by yourself.

Vik Olliver & Adrian Bowyer / CC BY-SA 3.0
RepRap project - Wikipedia
RepRap: Blog

So organisms seem to be the closest thing to real von Neumann constructors that we know to date. This has even been shown quite nicely by Jannie Hofmeyr who has mapped von Neumann's original design onto the biological cell (albeit with some important modifications, inspired by the work of Robert Rosen).

This is a brilliant paper bringing together a bunch of different concepts of "self-replication" that have been constructed over the decades (e.g. Rosen, von Neumann, Gantí) Hofmeyr, J. H. S. (2021). A biochemically-realisable relational model of the self-manufacturing cell. Biosystems, 207, 104463.

The simple observation that organisms make themselves is nothing new and goes back to philosopher Immanuel Kant in the 18th century. Kant highlighted that the parts of the organism are only there because they are somehow related to the whole organism.

Originally from Kant's 'Critique of the power of judgement.' Gambarotto, A., & Nahas, A. (2022). Teleology and the organism: Kant's controversial legacy for contemporary biology. Studies in History and Philosophy of Science, 93, 47-56. Link

Your neurons are there because you need to think and you have mitochondria because your cells and really your whole body needs energy. This is top-down causation back again.

Of course, the whole organism only exists because it's made up of parts. So together, we have this weird circular relationship that seems to be fundamental to life and completely foreign to physics.

Organisms, Agency and Evolution (p. 11) / Denis Walsh

I can't understate how strange this kind of causation is. It's something much deeper than a simple feedback loop or a recursive function.

If we want to use the metaphor to computing, it would not only be programmer and programmed, but also writer of the language the programmer is using and builder of the computer.

Doc Searls / CC BY-SA 2.0

If we want more of a mathematical metaphor, it would be like an equation that could write itself by adding in new terms and even new ways of mixing terms together with new axioms.

Either way, that is something we just don't know how to deal with. Somehow cause and effect are entirely wrapped up inside organisms in a way in which we haven't even begun to understand.

Originally from Kant's 'Critique of the power of judgement.' Gambarotto, A., & Nahas, A. (2022). Teleology and the organism: Kant's controversial legacy for contemporary biology. Studies in History and Philosophy of Science, 93, 47-56. Link

But one key consequence that we can get from this picture is that organisms have a sense of agency that puts them well beyond the domain of physics.

In classical physical systems, objects are always bound by laws and their possibilities are inherently limited. All the possible states of a system can always be described beforehand by what physicists call phase space.

I would suggest reading this whole chapter (at least) to get a better picture of why the current methods of physics are limited. Time Reborn, Chapter 4: Doing Physics in a Box (p.39) / Lee Smolin

But in biology, we again run into a problem. We can never define all the possible states of a system ahead of time.

Kauffman, S. A. (2014). Prolegomenon to patterns in evolution. Biosystems, 123, 3-8.

Say if I gave you this screwdriver, you could use it to tighten a screw, poke someone, pick your nose, stir your coffee, teach a class - the possibilities are literally endless. Or more precisely, we should say that they're indefinite. We can't prestate them in advance.

Roli, A., Jaeger, J., & Kauffman, S. A. (2022). How organisms come to know the world: fundamental limits on artificial general intelligence. Frontiers in Ecology and Evolution, 1035.

But if we can't define a phase space for the organism then we have no hope of coming up with a universal law. Because no matter what subset of possibilities we choose to describe with our law, we'll always leave something out that is possible for the organism to reach. Every model of the organism will always be incomplete.

Cortês, M., Kauffman, S. A., Liddle, A. R., & Smolin, L. (2022). Biocosmology: Towards the birth of a new science. arXiv preprint arXiv:2204.09378
Roli, A., Jaeger, J., & Kauffman, S. A. (2022). How organisms come to know the world: fundamental limits on artificial general intelligence. Frontiers in Ecology and Evolution, 1035. See Life Itself / Robert Rosen for the full argument.
Roli, A., Jaeger, J., & Kauffman, S. A. (2022). How organisms come to know the world: fundamental limits on artificial general intelligence. Frontiers in Ecology and Evolution, 1035.

So the future that organisms have is open in the deepest possible way. They are creative enough to construct futures that we could never imagine with any meaningful algorithm, equation or anything else.

They are agents in control of their own fate, not objects limited by the phase spaces of differential equations. And thus, the tools of physics are too limited to capture the whole organism.

Kauffman, S. A. (2014). Prolegomenon to patterns in evolution. Biosystems, 123, 3-8.

Science isn't about reducing everything to physics or fundamental laws of nature. Physics is just one very particular tool we apes have invented to understand reality. It's a useful tool no doubt, but it's not the most fundamental, or the most important, or the most-inclusive.

It's just one perspective.

Windows on Reality / Philip Kitcher

To even begin to understand the way the universe works with our limited brains, we need as many good perspectives as we can get. We want our toolbox to be full of different insightful ways to see the world, not just a hammer that reduces everything to the jigglings and wigglings atoms.

Perspectival Realism (p. 8) / Michela Massimi

Thanks so much for watching, this is the third video in a series on why biology is not mechanistic like physics, if you want to see the first part on the history of the debate click here and if you want to see why cells aren't machines you can watch the second part here.

A brief history of teleology in biology
Cells are not machines