Mark Twain may never have actually said it — that's fitting, because the idea is bigger than any one person. History doesn't repeat, but it rhymes. There is something underneath the surface particulars of any era, something structural, that keeps generating recognisable shapes. Tyrants who crossed the wrong line. Empires that ate their own foundations. Republics that hollowed out from within while the circus played on.
For most of human history, explaining these patterns has been the province of historians, philosophers, and storytellers. They have done the job beautifully. But they have not done it quantitatively. We can read Thucydides on the fall of Athens and feel the force of his analysis. We cannot, however, run his model on a new dataset.
The Complex Adaptive Model of Societies — CAMS — is an attempt to change that. Not to replace the historian's craft, but to sit alongside it; to give the rhyme a score.
The foundational move in CAMS is deceptively simple: treat a society the way physics treats any complex open system. Not as a collection of individuals, nor as a state apparatus, nor as an economy — but as a thermodynamic organism. Something that takes in energy, processes it, and either maintains coherent internal order or doesn't.
This is not a metaphor. The Nobel laureate Ilya Prigogine showed that ordered complexity can emerge and persist precisely through the continuous dissipation of energy in open systems — the same principle that distinguishes a living cell from a crystal, a hurricane from a rock. A society is one of these dissipative structures. It maintains itself far from equilibrium, and it does so through coordination.
The key question then becomes: what are the functional components that do the coordinating? Not the named institutions — not 'the Senate' or 'the Reserve Bank' — but the underlying roles that every persistent social organism must perform, regardless of the labels it attaches to them.
CAMS identifies eight. Eight is not an arbitrary number. It is the minimum topologically closed set that can sustain what complexity theorists call Kuramoto criticality — the condition where a distributed network achieves coherent synchronisation. Below eight, the system cannot replicate fractally across scales. Above eight, you have redundancy. Eight is the answer that falls out of the mathematics of social coordination.
The eight nodes partition neatly into two loops, distinguished by the timescale on which they operate:
The slow loop — Helm, Lore, Archive, Stewards — is the memory and governance layer. It changes on the timescale of decades or centuries. It is what a society believes about itself, how it governs, what it records, and how it cares for its population. The slow loop is the civilisational immune system.
The fast loop — Shield, Craft, Hands, Flow — is the material and operational layer. It changes on the timescale of years. It is how a society defends itself, builds things, labours, and moves resources around. The fast loop is the civilisational metabolism.
Every node can be measured across four dimensions: Coherence (internal alignment), Capacity (available energy and competence), Stress (load and strain), and Abstraction (the degree to which the node operates through symbolic rather than purely physical means — through plans, narratives, laws, beliefs).
These four dimensions are not just descriptive. Their mathematical relationships encode physical constraints. The most important is the Stress–Capacity anti-correlation: in any healthy node, when stress rises, capacity is being drawn down; they should move in opposite directions. This is Falsification Criterion One — if any newly assessed society shows a persistent positive correlation between stress and capacity in a given node, the thermodynamic constraint claim is weakened. Across 38 societies and multiple independent assessors, FC1 has held universally — with one structurally significant exception.
The Shield node — the defence and coercive function — consistently violates FC1. When stress rises in the Shield, capacity tends to rise with it. The system pours resources into the coercive apparatus precisely when that apparatus is most strained. This is not a measurement error. It is a structural fact about how societies relate to their security function.
CAMS interprets this as the Shield being a coercive-growth node: it feeds on threat. A society that is under external pressure, or that has developed a powerful military-industrial complex, will see its Shield grow precisely because the stress is there. This is not healthy coordination — it is a parasitic coupling. The Shield is the one node that can grow by consuming the system that hosts it.
History rhymes here with remarkable consistency. The late Roman legions. The Soviet military-industrial apparatus. The permanent war economy of twenty-first century America. In each case, the coercive function expanded under stress rather than adapting to reduce it. CAMS gives this pattern a number.
And there is a downstream consequence that Rome discovered and that every overstretched empire rediscovers. When the Shield grows large enough, it stops serving the Helm. It becomes the Helm. Or rather — it begins selecting the Helm. The Praetorian Guard did not begin as kingmakers. They began as bodyguards. But an emperor whose legitimacy rests not on the coherence of the civic system but on the personal loyalty of armed men is, structurally, a hostage to those men. The Guard elevated Claudius after Caligula's assassination. They murdered Pertinax after sixty-six days in office because he tried to restore discipline. In the third century CE — the Crisis of the Third Century — they produced, deposed, and killed emperors at a rate that makes the current American political cycle look positively stable.
The question CAMS forces us to ask, watching the United States in 2026, is: at what point does an executive whose coalition rests on personal loyalty rather than institutional legitimacy become subject to the same structural dynamic? When does the Praetorian Guard choose the next emperor?
Everyone reached for Caesar in 2015. The escalator, the crowd, the crossing of invisible constitutional lines. And January 6th sealed it — there was the Rubicon, the demagogue general bringing his forces to the capital.
But Caesar governed. Caesar was brutal, autocratic, and eventually fatal, but he was a reorganiser. He had the legions. He crossed the Rubicon because the system had narrowed to two options: seize power or die. And when he arrived in Rome, he addressed the structural failures that had produced the crisis.
Trump is Tiberius. Second emperor of Rome. Inherited a functioning system, grew paranoid and resentful within it, retreated to his island villa — Capri, Mar-a-Lago, the geography hardly matters — and governed by proxy, by letter, by loyalty test and purge. Increasingly disconnected from the machinery he nominally commanded. Increasingly surrounded by those whose primary qualification was personal fealty rather than competence.
The first term was the crossing. The second term is the island.
We are now two years into a second administration that has not reorganised the system — it has personalised it. The civil service, once the Archive node made flesh, has been systematically hollowed. The Lore node — the universities, the press, the institutional knowledge-makers — is under sustained assault, its Coherence fractured not only from within by polarisation but from above by deliberate delegitimisation. The Stewards node, the property-owning and capital-holding class, is receiving its bread and circuses in the form of tax arrangements and deregulation: bought, for now. The Hands remain restless, their structural stress unaddressed, their resentment redirected outward at the targets the Helm has nominated.
And the Shield is growing.
Not the military exactly — though defence expenditure climbs — but the broader coercive and loyalty apparatus. The informal Praetorian Guard of a system in Reactive Mode is not always uniformed. It is the inner circle of personal loyalists, the institutional leaders who have signalled their willingness to serve the person rather than the function, the advisors whose primary skill is surviving in proximity to power. This is the Guard that will, when the time comes, choose what comes next.
After Tiberius died at Capri in 37 CE, the Praetorian Guard elevated Caligula — young, apparently biddable, the last male of the popular Julio-Claudian line. He was not their considered choice. He was the least threatening option at the moment of transition. He descended rapidly into the particular madness that absolute power with no institutional constraint tends to produce.
After Caligula, they chose Claudius — literally found hiding behind a curtain in the palace, according to Suetonius. Claudius was considered a fool, a figure of ridicule, physically awkward and politically marginal. He turned out to be one of the more competent administrators of the principate. Not because the Guard chose wisely, but because the system still had enough residual capacity in its Archive and administrative nodes to function around whoever occupied the Helm, provided that person didn't actively destroy those nodes.
After Claudius came Nero. And Nero did actively destroy those nodes.
The structural lesson is not about individual character. It's about what happens to succession in a system that has replaced institutional legitimacy with personal loyalty. The selection mechanism breaks. The Guard — the loyalty apparatus — optimises for tractability, not competence. It selects whoever is least threatening to the current balance of power within the inner circle. And that selection criterion is structurally independent of, and often in direct opposition to, the question of who is capable of addressing the system's actual coordination failures.
The American succession problem is visible in the data. A Helm node that has been personalised to the degree we are observing — where loyalty to the person is the primary criterion for proximity to power — cannot produce a coherent institutional succession. When the transition comes, whether through election, through the Twenty-Fifth Amendment, through the ordinary passage of time, the question of who comes next will be answered not by the civic system but by the loyalty apparatus that has accumulated around the current Helm.
The options are, structurally, Claudius or Nero.
Claudius: a figure that the Praetorian Guard considers safely marginal, who turns out to have enough residual capacity in the system's administrative and institutional memory to hold things together — not because they govern brilliantly, but because the Archive hasn't been completely destroyed yet, and competent administrators can work around a manageable Helm.
Nero: a figure who completes the personalisation, who dismantles the remaining institutional nodes in the pursuit of pure performance of power, and who produces the conditions for the full phase transition — reorganisation under external pressure, fragmentation, or the emergence of an entirely new systemic configuration.
CAMS cannot tell you which one comes next. It can tell you that the system's current trajectory — declining Helm Coherence, growing Shield parasitism, Archive degradation, Lore fracture, Hands unaddressed — is producing exactly the structural conditions that make the Claudius/Nero binary the relevant question.
Rome is the case study that keeps coming back, and for good reason. The Roman trajectory from republic to principate to late empire is one of the most complete datasets available for studying civilisational phase transition.
At its height, Rome had extraordinary Capacity across most nodes. It had legal coherence (Archive), military dominance (Shield), a functioning welfare system (Stewards), and an Abstraction layer — the idea of being Roman — that provided civilisational glue across an enormous territory. Critically, it had access to the wheat surplus of Egypt, which functioned as a low-cost energy subsidy for the urban proletariat, suppressing the social stress that might otherwise have triggered faster collapse.
But the Stewards node was failing. The landowning class had progressively consolidated agricultural land, dispossessing the peasant farmer class that had historically formed the backbone of both the legions and the civic body. The dispossessed flooded the cities. The urban proletariat swelled. Bread and circuses were not cruelty — they were a rational response to a coordination crisis that the slow loop could no longer absorb.
The republic's institutional architecture could no longer process the contradictions that had built up. Caesar's crossing was a phase transition: the system reorganised under military governance because civilian governance had lost the Coherence to function.
And then came the principate. And then came the Guard. And then came the choices.
The question CAMS asks of the present is precisely this: are we watching a pre-transition accumulation? Is the slow loop — governance, civic memory, welfare, normative coherence — losing its capacity to absorb the stresses that the fast loop keeps generating?
The data, as of April 2026, suggests the accumulation is well advanced. The American system health score sits at 1.46 — matching the Great Depression. Not as a metaphor. As a measurement. The same pattern of Coherence breakdown, Stress overload, and Abstraction Inversion — where the symbolic systems of politics, media, and finance have floated so far from biophysical and economic ground truth that the Helm is effectively governing a narrative rather than a nation.
One of the more surprising findings of the CAMS research programme is how far down the phylogenetic tree the eight-node structure goes. Dolphin pods use tools — sponges held in the mouth to protect the snout when foraging on abrasive seabeds. This is a Craft function. The behaviour is culturally transmitted, node-specific, and differentiable from foraging (Hands) and coordination (Flow) behaviours.
Chimpanzee troops exhibit rudimentary versions of all eight CAMS nodes: alpha coalitions (Helm), raiding parties (Shield), grooming norms (Lore), observational learning (Archive), foraging groups (Hands), tool use (Craft), food sharing (Flow), and alloparental care (Stewards). The architecture predates Homo sapiens.
Even slime moulds — Dictyostelium — when stressed, aggregate from independent amoebae into a multicellular organism with differentiated functions. This is Kuramoto coupling made biological. The same physics operates at every level.
This is not anthropomorphism. It is the recognition that evolution acts on any gradient of coordination in an ecology, and that the solutions it finds keep converging on the same architecture — because the architecture is not biological. It is physical. It is what any dissipative structure looks like when it achieves stable, persistent, internally differentiated order.
And it tells us something important about the Praetorian dynamic. The Guard is not a Roman peculiarity. It is what the Shield node produces when Helm Coherence drops below the threshold required to maintain deliberative governance. The troop selects the alpha. The alpha controls the troop. The question of whether the troop selects well is answered not by the troop's wisdom but by the structural conditions of the system at the moment of selection.
The chest-beating, the dominance display, the tariffs-as-territorial-signalling — this is not aberrant behaviour. It is primate behaviour, fully continuous with our evolutionary inheritance, activated when the system's free energy budget drops below the threshold required to sustain deliberative cognition. When stressed organisms cannot think their way through the problem, they feel their way through it. And feeling, at the Helm, looks like reactive dominance.
The current CAMS corpus spans 38 societies, multiple assessors (Claude, Grok, Gemini, GPT variants), and over 8,000 scored data points. Several findings have achieved sufficient consistency to be stated as structural results:
System Affect — the net energetic margin across all nodes — is the dominant predictor of viability, with a correlation of approximately r = 0.87 against the Viability Function Ω. Before you know anything about a society's specific institutional arrangements, the simple question of whether it has more collective energy than collective strain predicts its trajectory with remarkable accuracy.
The Library archetype is the universal attractor. Across all tested societies, regardless of regime type, the configuration that represents high Archive coherence, moderate Helm stability, and functional Lore–Archive coupling is where viable systems tend to converge. Societies that destroy their knowledge-preservation function — their Archive — move systematically toward fragmentation.
Mutual escalation between major powers is structurally self-defeating. When two high-Shield societies enter competitive mobilisation, the Shield anomaly and the Torsion metric both predict deteriorating system health for both parties. There is no CAMS dataset in the corpus where sustained military rivalry has produced long-term viability gains for either side. None.
This last finding has obvious contemporary resonance. The current global discourse around geopolitical competition — the language of necessary confrontation, civilisational struggle, mutual deterrence — appears through the CAMS lens as a collective coordination failure in which the Shield anomaly is being deliberately amplified by actors on multiple sides, to the detriment of the system health of all parties involved.
Including the party that currently controls the most powerful Shield in human history.
Strip everything away and CAMS comes down to this: every social organism — from a termite nest to a Roman empire to a modern nation-state — is trying to solve the same problem. How do you keep eight essential functions coordinated, energised, and coherent, across timescales from the daily to the century-long, under continuous internal and external stress?
When it works, you get what CAMS calls high System Affect: the collective energy of the organism exceeds its collective strain, and the slow loop maintains enough coherence to absorb shocks without fragmentation. When it fails, the fast loop begins cannibalising the slow loop. The military eats the culture budget. The market erodes the archive. The governing function loses the legitimacy that Lore once provided. And the system tips toward a phase transition.
Two years into Trump's second term, the slow loop is being systematically cannibalised. The Archive is degrading. The Lore is fracturing. The Helm is personalised to the point where institutional succession has become structurally dependent on the loyalty apparatus — the Guard — rather than on civic process.
The Praetorian Guard will choose. It always does, when it reaches this point. The only question history has never been able to answer in advance is whether it will choose Claudius or Nero.
CAMS cannot answer that question either. But it can tell you — with the precision of a body temperature reading, with the objectivity of a vital sign — that the system is sick, that the therapeutic window is finite, and that the rhyme, this time, is one we have heard before.
History doesn't repeat. But it rhymes.
And right now it is rhyming with something that should concentrate our attention.
Kari Freyr McKern is an Australian writer, librarian, and retired IT manager, and the originator of the CAMS (Complex Adaptive Model of Societies) framework. Neural Nations is her ongoing project in civilisational analysis.