This post spun out from my reading log.

Every now and then, I hear about What is Life? The Physical Aspect of the Living Cell (1944) and I remember how awesome it sounds and how much I would like to read it. Though I’ve never had a copy on my bookshelf, I consider this a good example of one of the predictably deep books on my shelf I systematically haven’t read. Well, that was the old me. I resolved to be no longer afraid to throw myself into deep ends. When the book came up again recently, I took my chance and started listening immediately. It wasn’t long into the introduction before I knew I had made the right choice.

I would divide the contents of the book into a discussion and resolution of three apparent contradictions. Though the bulk of the book and its legacy is concentrated on the first of the three contradictions (concerning the stability of the genetic material), the second (concerning life’s ability to resist entropy) was what drew me to the book in the first place, and the third (concerning free will) was of some interest.

Regarding the first of the apparent contradictions. From the perspective of a physicist in 1944, living organisms and their evolution were quite mysterious phenomena:

1. On the one hand, based on our understanding of thermodynamics, we know that the apparently orderly laws of physics governing macro-scale systems are only orderly as a consequence of the massive numbers of atoms involved. In any small groups of atoms, physics is unpredictable, unstable, chaotic, with atoms bouncing around and colliding randomly. If you zoom out to a large enough group of atoms, the central limit theorem kicks in and on the whole, variance away from the average physical tendencies vanishes, leaving only predictable diffusion of energy or molecules.

2. On the other hand, in the course of the cycle of life, organisms maintain and transfer to their descendants some physical material that goes on to determine all aspects of their form and function. This hereditary material is stored in the chromosomes within the nucleus of each cell, which amounts to a small number of atoms from a thermodynamic perspective. Nevertheless, apart from a small rate of mutations these small groups of atoms are able to reliably govern the form and function of organisms on timescales spanning many years.

Schrödinger’s resolution to the apparent contradiction of the stability of these small groups of atoms, in light of his understanding of quantum mechanics and some existing work in experimental biology, is as follows. He conjectures that the hereditary material comprises a structure of matter not before studied by physicists, with the stability of a molecular crystal but with an aperiodic rather than repeating structure that allows it to function as a hereditary medium. Moreover, the molecules forming the code are largely stable while still allowing rare mutations that facilitate evolution by the existence of quantised states between which the molecules can transition during rare events, but within which they otherwise remain.

The majority of the book is concerned with outlining the above contradiction and reviewing the biological evidence leading to Schrödinger’s conjecture. This was the main thrust of the book and is also the basis for its main claim to fame, as less than a decade later, Schrödinger’s conjecture would be proven correct upon the discovery of DNA by Franklin, Watson, and Crick. Both Watson and Crick attributed part of their inspiration to enter the field of molecular biology to reading What is Life?

But, as I said, this is not what brought me to the book. I wanted to read the book for what turned out to be a brief discussion towards the end, of a second apparent contradiction, concerning life and thermodynamics at the macro-scale rather than the micro-.

1. On the one hand, we have the observation that according to the second law of thermodynamics, all closed systems tend towards a maximally disordered state.

2. On the other hand, organisms resist this tendency and maintain themselves in a state of low entropy over their lifetimes.

The resolution to this paradox is simpler: the organisms are not living in a closed system, but are in fact exporting entropy to their environment, or, as Schrödinger puts it, “drinking orderliness” (negative entropy or, more accurately, free energy). The “orderliness” in turn is supplied ultimately to the Earth by the sun, and a full accounting of entropy exchanges between all relevant parties will leave the second law upheld.

This much, I had concluded after studying thermodynamics during undergrad, but it was still satisfying to finally see this famous rendition. Schrödinger also pointed out that the organism’s ability to concentrate a stream of order into itself is also downstream of the hereditary material, based on which the entire organism is of course constructed.

Finally, we have in the epilogue a discussion of the topic of free will. A third apparent contradiction is raised:

1. In the case of we humans, the physicist sees that our bodies are made of atoms that function mechanically according to the laws of nature.

2. Yet, we know, by “incontrovertible direct experience,” that we control and take responsibility for our motion and actions.

The resolution that Schrödinger suggests is simply to define ‘we’ as that which moves the atoms by the laws of nature. It follows that the apparent plurality of consciousness is an illusion, and all consciousness is merely different aspects of one singular thing.

I thought this was an interesting take, pleasant, though not compelling. I remain, like everyone else is as far as I can tell, very confused about consciousness on a technical level. On that note, Schrödinger does not seem to be hopeful—here’s a nice passage from earlier in the book:

[Life] is a marvel than which only one is greater; one that, if intimately connected with it, yet lies on a different plane. I mean the fact that we, whose total being is entirely based on a marvellous interplay of this very kind, yet possess the power of acquiring considerable knowledge about it. I think it possible that this knowledge may advance to little short of a complete understanding of the first marvel. The second may well be beyond human understanding.

What did I learn from this book that is of relevance to AI safety? On a technical level, I already knew most of the ideas from statistical mechanics. I knew a little about genetics and evolution, though the book revealed that I don’t know that much: I learned that heritable mutations are rarer than random mutations and for good reason from an evolutionary search perspective. I think this is a basic and well-known fact about evolution, but it was new to me. I should study some evolutionary biology, I am sure it would be good for me.

What I’m taking away from the book is more that it’s an example of both the power of deep scientific understanding and of science communication—two topics close to my heart. Schrödinger applied a mastery of the principles discovered in the field of physics to extrapolate beyond his field’s historical subject matter and make definitive predictions about an important scientific question. We could use some more of that kind of thing in the field of AI.

Moreover, in doing so, Schrödinger brought attention to a promising line of biological research and helped inspire a generation of physicists to get into molecular biology, seeding new discoveries and progress. In a sane world—one where we get the time we need to navigate the transition to a world with advanced AI systems—it will take an all-out, multi-disciplinary, multi-generational effort to prepare ourselves intellectually. We need visionary teacher-leaders to see far ahead of us and chart the course we need to take. Let Schrödinger be our example as we aspire to rise to this challenge.