Information and Intelligence
Neil D. Lawrence
2026-10-12
The Stokes Society, Pembroke College
Perpetual Motion and Superintelligence
1925: Motor vehicles (no perpetual motion)
2025: Promises of superintelligence singularity
Same fundamental impossibility?
Why Perpetual Motion Failed
\[\frac{\text{d}H}{\text{d}t} \geq 0\]
Entropy always increases
No motion without entropy production
No work without energy input
An Equivalent Statement for Intelligence?
Maxwell’s Demon:
“Intelligent” entity that violates 2nd law
Resolution: Landauer’s principle?
Information erasure requires energy
Implication
Intelligence has thermodynamic cost
Information processing has physical limits
What Intelligent Systems Must Do
Acquire information (sensing)
Store information (memory)
Process information (computation)
Erase information (memory mgmt)
Act on information (output)
What is the thermodynamic cost?
Landauer’s Principle
Erasing 1 bit requires: \(Q \geq k_B T \log 2\)
Not engineering limitation
Fundamental thermodynamic bound
Entropy must go somewhere
At room temperature: \(\sim 3 \times 10^{-21}\) Joules/bit
Thermalisation from Different Initial Conditions
9 balls on a \(3 \times 3\) grid;
Different starting conditions.
Nine billiard balls on a 3×3 grid. The histogram grid tracks each ball’s cumulative \((v_x, v_y)\) velocity distribution. Entropy per ball rises from near zero (single bright dot at the initial velocity) to the Maxwell–Boltzmann value as collisions thermalise the gas. Use the Initialisation dropdown to compare directional starts (all balls move the same way) with propellor starts (adjacent balls move in opposite directions): all initial conditions converge to the same equilibrium, demonstrating ergodicity.
Jaynes and Maximum Entropy
Ed Jaynes who developed the maximum entropy principle
Maximum Entropy Motivation
Jaynes (1957) : Statistical mechanics as inference with incomplete information
Maximum entropy principle: maximise uncertainty given constraints
Avoids unwarranted assumptions beyond available data
Dice Example
Dice example: Average result 4.5 instead of 3.5
Constraints:
\(\sum_{n=1}^6 P_n = 1\) (normalization)
\(\sum_{n=1}^6 nP_n = 4.5\) (observed average)
Interactive die-roll simulation. Click the die or press Roll to sample from the configured distribution. The histogram shows empirical relative frequencies (coloured bars) overlaid on the theoretical probabilities (dashed outlines). Use the sliders to set arbitrary outcome weights, or click a preset to load the uniform distribution (mean 3.5), the Jaynes maximum-entropy distribution (mean 4.5), the simple 50/50 distribution (faces 4 and 5 equally, mean 4.5 with minimal entropy), or a low-biased distribution (mean 2).
Sampling Two Dimensional Variables
Correlation
Correlation is when two variables are dependent
Sampling Two Dimensional Variables
Independent Gaussians
Two independent Gaussians for the \(x\) and \(y\) velocity of a ball.
The Classical Observer
Here the observer is monitoring the movements of the particles. We’ve plotted the velocities alongside the 1 standard deviation contour of their theoretical distribution.
The Munchkin Provision
So there’s a board game called Munchkin — it’s a card game I used to play with my kids. You have cards that battle each other. The interesting thing about this game is that it explicitly says in the rules that the rules can be inconsistent. There’s a set of written rules, and then there are cards which have different rules on them.
The Munchkin card came has both cards and rules. The game explicitly acknowledges that this can lead to inconsistencies which should be resolved by the game owner.
Munchkin Card Game
And it says: if the rules are inconsistent, any other dispute should be settled by loud arguments, with the owner of the game having the last word. And it occurs to me that the Munchkin provision is a property of almost every game or activity we engage in — there has to be an arbitrator to settle how the rules go. But you can reverse that and say: a self-governing system cannot refer to external arbitration. That’s a tautology. If you want a self-governing system, it can’t ask the owner of the game what to do next. And the interesting thing I want to explore today is whether there’s anything interesting in that tautology that we can use to say something about self-governing systems.
Rules may be inconsistent … so …
Any other disputes should be settled by loud arguments, with the owner of the game having the last word.
Munckin Rules (Jackson, 2001)
A Tautology
Self-governing systems cannot refer to external arbitration.
The No-Barber Principle
So I’ve got three papers in this series so far, and the third paper is actually about this. It talks about what I call the no-barber principle, which is inspired by Russell’s paradox — the idea that the barber shaves everyone in the village apart from those who shave themselves, followed by the question: does the barber shave themselves? In set theory it’s a question around the set of all sets that don’t belong to themselves. This leads to what one would call impredicative circularity. If the barber does shave themselves, then the rules say they don’t; if they don’t, the rules say they do.
Russell’s Barber Paradox:
Barber shaves all who don’t shave themselves
Does the barber shave themselves?
Paradox: Definition includes itself in scope
No External Adjudicators
Forbidden:
External observer
Pre-specified outcome space/Hamiltonian
Privileged decomposition
External time parameter
No appeal to structure outside the game
That’s the sort of thing we want to forbid. And that’s what motivates the no-barber principle. The no-barber principle basically says we want to be in a situation where there are no external adjudicators. That means no external observer, no predefined outcome space, no external time parameter, and no privileged decomposition in the game. Nothing dictated from outside. And I’ll give you a very disconnected sense of how this manifests. Imagine if you had an external time parameter in the game, and as part of that game an entity’s time parameter was manipulated so it could move in time. A time travel paradox has the same impredicative circularity feel as Russell’s paradox — went back in time, met your mother, do you continue to exist? And that seems to come from someone outside the system playing with the time. If something emerged consistently inside the system, that shouldn’t be able to happen. So the idea is to create a game where you’re not appealing to any structure outside the game.
The Three Axioms
What they show is that from three axioms — functoriality (information loss adds when you compose processes)
\[F(f \circ g) = F(f) + F(g)\]
Information loss is additive
Compose processes → add losses
Convex Linearity
Convex linearity (if you choose between two processes with probability lambda, the information loss is the weighted sum)
\[F(\lambda f \oplus (1-\lambda)g) = \lambda F(f) + (1-\lambda)F(g)\]
Probabilistic mixture of processes
Linear in probability weights
Continuity
And continuity — from those three axioms alone, the unique form for information loss is the Shannon entropy difference, scaled by some factor.
Small change in process
Small change in information loss
\(F(f)\) continuous in \(f\)
The Main Result
Three axioms \(\Rightarrow\) unique form: \[F(f) = c(H(p) - H(q))\]
Information loss = scaled entropy difference
Shannon entropy emerges from axioms
No other measure satisfies all three
I really like this because it appeals to some idea I’d like to be true: that entropy is more fundamental than probability. Probability always asks what will happen, what does happen. Entropy, especially in things like channel coding, gives you impossibilities. Impossibilities are much more robust than predictions. That’s one reason I’m fascinated by entropy, though I’m probably less expert in it than everyone else in the room.
The Inaccessible Game Setup
So what does the no-barber principle help us with? If I want to avoid external structure, and I now have a mechanism for representing information loss, what I want to do is enforce information conservation. If we have defined a form of information loss, it feels like we can now isolate the game from observation or interaction — we can say that no external observer can extract or inject information. The aim is to build a game in the following way: a representation of information loss and a prohibition of information exchange with the game. I’m certainly not doing this perfectly, but that’s the sort of thing I’m aiming for. It’s like a selection principle for the mathematics I want to use in the game.
Avoid external structure.
Represent information loss
Enforce information conservation
Marginal Entropy Conservation
And then the claim is that the sum of those marginal entropies is conserved. I haven’t seen this type of constraint before. And I sort of pause there — everything falls from that. If it’s flawed in some way, everything else I’ve done collapses, but don’t let that make you shy about criticising it.
\[
\sum_{i=1}^N h_i = C
\]
Isolation: cf energy conservation — but for information
The reason I want it to be this atomic form is a notion of exchangeability amongst the game’s variables. If I start talking about interactions, I think there’s a danger of breaking that. It’s also an extensive property — it feels like the type of property where in the future I could take it to infinity and do something non-parametric. I haven’t done that, but I’m not ruling it out. And I don’t know what the underlying dimension is — that would be an external thing. The aim is to isolate the system, which will prevent barbers from intervening.
So why was I looking for something like this? Well, in these kinds of systems, if you look at how effective rules emerge in things like physics, energy conservation tends to be a thing. There has to be something conserved — some constraint.
The Classical Observer - Inaccessible
Here the observer is blocked from monitoring anything inside the sytem.
Joint Entropy
We don’t see see the outcome space
But we know it has a joint entropy
Now imagine that the observer is not integrated. They cannot see inside the system. They don’t have access to the outcome space. We don’t see the individual outcomes; we just know there’s a joint entropy associated with the system. The observer has a marginal entropy for each variable they interact with, but they don’t have access to the joint. This is the inaccessible part — the inner workings are hidden. The observer has their own perspective, not direct access to the internals of the game.
The \(I + H = C\) Structure
So here’s the key relationship. From \(\sum_i h_i = C\) , with a little algebra — using the fact that for a joint distribution the joint entropy equals the sum of marginal entropies minus the multi-information — I can show that \(I + H = C\) .
\[
\sum_{i=1}^N h_i = C
\]
What does this conservation imply for dynamics?
Analogy to classical mechanics
Energy: \(V + T = E\)
Information: \(I + H = C\)
System “rolls downhill” from correlation to disorder
Think of it like potential energy and kinetic energy: the correlation is potential energy, the entropy is kinetic energy. In equilibrium you’d have an equal mix. But we start in a highly correlated state — that’s what I mean by the origin — and the system evolves to maximize entropy.
So now I have the game. I’ve got \(I + H = C\) . And I want the dynamics of the system to maximise \(H\) . But to set up what those dynamics look like, I need to parameterise the configuration space.
Lawvere Diagonalisation
Impossibility results sharing a structure:
Russell’s paradox
Cantor’s theorem
Gödel incompleteness
Turing’s halting problem
Tarski’s undefinability
Unified by Lawvere diagonalisation (Lawvere, 1969)
The Five-Move Recipe
Lawvere’s Five-Move Recipe:
Rules: operations from inputs to outputs
Universal evaluator: run any rule on any input
Internalise syntax: rules can reference all operations
Self-application: rules can serve as their own input
Twist: negate or complement outputs
When all five hold: contradiction is derivable
The Barber Paradox as Lawvere Diagonalisation
Barber as Lawvere:
Rules
shaving rules \(R\)
Evaluator
\(\text{shaves}((R,p),q)\)
Internalisation
each person \(p\) carries rule \(R_p\)
Self-application
\(R_p(p)\)
Twist
\(T(p) = \neg R_p(p)\)
\(\Rightarrow\) contradiction: \(\text{shaves}(B,b) = \neg\text{shaves}(B,b)\)
Blocking Diagonalisation by Blocking Copying
Blocking the Construction:
Self-application requires cloning : \[\Delta : A \to A \times A, \quad \Delta(a) = (a,a)\]
Cartesian category : canonical \(\Delta\) exists — Lawvere diagonalisation possible
Symmetric monoidal category : no canonical \(\Delta\) — self-application step fails
Removing free copying blocks the diagonal construction
Linear Logic and No-Cloning
Two programmes that block copying:
Linear logic (Girard, 1987) : * Assumptions are resources — can’t duplicate freely * Cartesian \(\to\) symmetric monoidal
Quantum probability (no-cloning) : * No canonical \(A \to A \otimes A\) for unknown states * Noncommutative \(C^*\) -algebras replace Boolean event spaces
Both satisfy the no-barber constraint for independent reasons
Energy Constraints
Normally we derive physical laws by
Maximise entropy subject to energy conservation
Marginal Entropy Conservation
\[
\sum_{i=1}^N h_i = C
\]
Entropy Constraints
Maximise joint entropy subject to marginal entropy conservation
Energy
In certain thermodynamic limits:
Marginal entropy conservation \(\equiv\) Energy conservation
See Lawrence (2025)
Maxwell’s Demon
Maxwell’s demon was designed to highlight the statistical nature of the second law of thermodynamics.
Maxwell’s Demon. The demon decides balls are either cold (blue) or hot (red) according to their velocity. Balls are allowed to pass the green membrane from right to left only if they are cold, and from left to right only if they are hot. The displayed entropy is the Shannon entropy of the velocity histogram (a coarse-grained proxy, not full thermodynamic entropy).
Conclusion
Introduced inaccessible game
Framework for studying information isolation
A selection principle for a self-adjudicating system?