Thermontology
2026-09-02
2.0.1 Without further ado, let's actually start thinking about physics.
2.1.1 First I'm gonna describe a "baseline physicalist computational-functionalist worldview", which is, IMO, a very powerful and predictive way of seeing the world.
2.1.2 Firstly, physicalism. Here are the main tenets of (my preferred version of) physicalism:
2.1.2.1 Everything that exists is physical. Things are either primitive physical entities such as strings or quantum fields, or are composites made up of the primitive entities. This includes minds. There exists a precise mathematical formalism describing the primitive entities(which we may not fully know yet)
2.1.2.2 Everything that happens is due to the laws of physics, which are mathematical equations which dictate the evolution of the state of the primitive entities(in some cases probabilistically).
2.1.2.3 The universe has a finite past and began in a simple low-entropy state. Mind-possessing things like humans and animals are the result of evolutionary processes.
2.1.2.4 The laws of physics are computable, meaning they can be evaluated using a Turing machine. Thus everything that exists in reality can be emulated on a computer. You could think of reality as running on a big Turing machine.
2.1.2.5 We actually know explicitly the laws of physics determining everything relevant to everyday life, including the functioning of the human mind.
2.1.3 I think this worldview is a great one. Using it, you can make many correct predictions and observations.
2.1.3.1 It's worth thinking a bit about how we got here. Back in the day, it wasn't clear that everything was physical, or that uniform physical laws existed, although some people(such as Democritus) held that the world was solely physical.
2.1.3.2 Newton's derivation of the elliptical movement of the planets was the first big success for precise mathematical laws. Other disciplines such as chemistry explained other parts of the world and were gradually shown to be consistent with a single set of physical laws.
2.1.3.3 The sheer age of the universe and Darwinian evolution explained how complex structures such as humans could come to exist from simple initial conditions.
2.1.4 While the physicalist worldview is a very powerful one, it is lacking some things which one would need from a comprehensive theory of reality. One prominent issue: the relation of our experiences and minds to the physical state is not clear.
2.1.4.1 One powerful theory of the mind within physicalism is computational functionalism. This philosophy holds that the mind can be thought of as an algorithm running on the hardware of our brain. Subjective experiences, thoughts, etc. emerge from, and have functional roles within, this algorithm. In principle, the same algorithm could be run on different hardware and give rise to the same mental states.
2.1.4.2 This is roughly the dominant view of the mind around these parts(i.e. within rationalist-adjacent circles). However, taking it very seriously can lead to some strange places...
2.1.4.2.1* (exploration of odd rationalist metaphysics; bit of a tangent) If the same algorithm can be run on different hardware yet give rise to the same experience, this opens up the possibility that we could be in a simulation. How should we allocate probability between the different possible copies? Even worse, there are seemingly infinitely many possible ways of interpreting physics as 'performing computation' and hence infinitely many copies of us.
2.1.4.2.2* This, combined with Bayesianism and the theory of Solomonoff induction, naturally leads one to assign a weighting to different copies based on their algorithmic complexity. At this point, it is tempting to discard the notion of a privileged physical reality altogether, regarding "reality" as simply one of an infinity of simplicity-weighted mathematical structures in which we happen to be instantiated.
2.1.4.2.3* Pondering decision theory can lead to the further radical step of abandoning the algorithmic weighting over mathematical structures, re-interpreting it in terms of preferences. In this metaphysics, the only real things are your present existence, the decisions you can make, and your utility function over all possible mathematical structures. Having reached this point, however, fundamental issues remain(where does your utility function come from? How does your "mathematical intuition" decide which actions will lead to which consequences?) and it is difficult to see how to make further progress.
2.1.5 Other problematic areas in physicalism include the interpretation of quantum mechanics(MWI is a pretty good response IMO) and the exact relation between the base laws and higher-level entities(related to the computation-physics correspondence problem above; there are a variety of plausible approaches one can take). Seemingly, there are no fundamental issues here...
2.1.6 I will be interrogating physicalism from a somewhat skew perspective to the above, asking the question:
2.2.1 For those not familiar, the Game of Life is a simple dynamical system invented by John Conway in 1970. It consists of a grid of squares either in an "alive" or "dead" state.
2.2.2 The grid has the following evolution rules(where "neighbors" = adjacent cells, including diagonally adjacent):
2.2.2.1 A live cell stays alive in the next time step if it has 2 or 3 live neighbors; otherwise it dies
2.2.2.2 A dead cell becomes alive if it has 3 live neighbours; otherwise it remains dead.
2.2.3 Despite the simplicity of its rules, the game of Life is famous for hosting a variety of intricate structures.
2.2.3.1 One example is the glider, which moves one cell diagonally from its starting point once every 4 steps(for all figures in this section, click to animate)
2.2.3.2 There are also a wide variety of stable oscillators. Here's a period-3 "star" oscillator:
2.2.3.3 Individual patterns can be assembled into more complex ones. Here's a "glider gun", a structure which produces gliders:
2.2.4 There are other cellular automata with simple rules but rich emergent structures.
2.2.4.3 Arbitrarily more complex patterns can be constructed. All 3 cellular automata are in fact Turing complete, so they can run any computation in principle.
2.2.4.4 There are many, many other cellular automata, and more generally discrete mathematical structures, with similarly rich emergent structures. A fun website exploring some is MCell.
2.2.5 Could the game of Life(the automaton) support life(self-replicating intelligent creatures)? There seems to be nothing that we know of forbidding it.
2.2.5.1 Of course, in a trivial sense we could use the GoL to run a Turing machine emulating the laws of physics. A non-trivial statement would have to include reasonably "natural" initial conditions and a "natural" way of locating the entities within the GoL.
2.2.5.2 Or if not the GoL itself, do any of the similar cellular automata do so? Or more generally, any of the discrete computational structures with interesting emergent properties?
2.2.6 On the surface it seems plausible. Say this were true. This would then pose, for physicalist-computational-functionalists, the question: why don't we live in such a universe?
2.2.6.1 What I mean by this is: our universe's laws are very mathematically special compared to those of a simple cellular automaton.
2.2.6.1.1 Compared to the GoL, the laws of physics are reversible in time, an important property(although some cellular automata share this property, like Critters). More generally, the classical state-space is a symplectic manifold and the laws preserve a symplectic form.
2.2.6.1.2 Our universe has continuous time and space.
2.2.6.1.3 The laws of physics have many global symmetries(time-translation, space-translation, rotation, Lorentz boosts). The form of the laws ensure that each such symmetry gives rise to a conserved quantity. They also have even more restrictive local, or gauge symmetries.
2.2.6.1.4 Most weirdly of all, the universe is quantum-mechanical in nature, giving rise to a vast enlargement of the size of the state-space we must consider(to complex-valued functions on the "normal" configuration space, roughly speaking), plus an odd notion of 'measurement' which defies our usual intuitions.
2.2.6.2 So if a simple cellular-automaton-like universe could support life and the algorithms that give rise to sentience, why do we live in such a mathematically rich universe, rather than a simple one? A priori, a simpler universe seems, well, simpler.
2.2.7 Having pondered this question for a while, I've come to think that there are plausible reasons that our laws of physics might be more amenable to life and "complexity" than a random -- or any -- cellular automaton or other simple computational system. In the course of doing this I've also adopted a philosophy of how consciousness and the mind work that's pretty different from computational functionalism. In the rest of section 2 I'll be reviewing in more depth some of the features of our physical laws that strike me as especially likely to be important for the existence of life and sentience.
2.2.8* (tangential point) Some readers may be wondering whether the question in 2.2.6 actually makes sense. Does there really have to be a "reason" that the laws are mathematically rich? Isn't this teleological thinking? Why couldn't it just be a bare fact that the laws are the way they are?
2.2.8.1* I believe that a justification can be given in terms of Occam's razor. The laws are the way they are; separately, we know that we exist. If we can deduce that certain special properties of the laws are required for life and sentience -- or perhaps that they simply make life much more likely -- we can compress our representation of the laws, taking those features for granted since we already know we exist. This represents an overall compression(and thus improvement) of our world model.
2.2.8.2* That being said, my real reason for inquiring here was simply a raw feeling that there must be a reason the laws of physics are so weird, damn it.