Early development in brains and bodies involves periods of high plasticity that gradually canalise into more stable structures. Too little plasticity prevents adaptation; too much, for too long, prevents reliable function. Critical periods are windows where this balance is particularly delicate.

As lakes, climates or markets approach a regime shift, they recover more slowly from small disturbances and show rising variance and autocorrelation. They still return to order, but more noisily and sluggishly, signalling that they are near a fragile edge where small events can, under the right conditions, snowball into large‑scale transitions.

At phase transitions – such as magnetisation or the onset of turbulence – small parameter changes produce large qualitative shifts. Near these points, systems blend emergent structure with large fluctuations, occupying a regime that is neither perfectly ordered nor fully disordered, so that local fluctuations can sometimes cascade into global reorganisation.

Ecosystems like coral reefs or lakes can flip between distinct regimes (e.g. coral‑ vs algae‑dominated, clear vs turbid). Diverse, well‑connected communities tend to occupy a resilient middle ground; loss of diversity or feedbacks can push them towards brittle, easily tipped states, where local disturbances can ripple outward and transform the whole system.

Many technological and biological networks evolve to be robust to common, expected shocks yet fragile to rare, poorly anticipated ones. Design choices about modularity, redundancy and coupling tune where the system sits between tightly integrated efficiency and loosely coupled resilience, and mis‑tuning can let failures percolate from one module to many.

Classical virtue ethics locates virtues between excess and deficiency: courage between rashness and cowardice, generosity between wastefulness and stinginess. This is a normative expression of dynamic symmetry, where good character avoids both rigid self‑denial and reckless indulgence, and individual acts can gradually tilt a life towards one extreme or the other.

Constitutional democracies balance stable rules and rights with mechanisms for revision and dissent. Too much centralised control stifles correction; too much fragmentation undermines coordination. When checks and balances weaken, abuses or crises in one part of the system can propagate through courts, media and parties, destabilising the wider order.

Effective collective reasoning avoids both groupthink and pure cacophony. Formats such as citizens’ assemblies and juries try to stabilise shared procedures while preserving space for disagreement and minority views. In such settings, well‑framed arguments or pieces of evidence can, for good or ill, spread stepwise through the group and shift the overall outcome.

Financial systems depend on a mix of liquidity, competition and constraint. Regulatory regimes that are too tight can freeze useful innovation; those that are too lax can amplify bubbles and crashes. In over‑leveraged or poorly regulated markets, small shocks can propagate through balance sheets and expectations, triggering self‑reinforcing waves of buying or selling.

Resilient supply chains combine standardisation with redundancy and local flexibility. Over‑optimised “just‑in‑time” systems can be brittle when conditions change; entirely ad hoc arrangements waste resources. When buffers and alternatives are missing, a single disrupted node – a factory, port or platform – can set off knock‑on disruptions across regions and sectors.

Agile, lean and other iterative methods replace both rigid, long‑range plans and total improvisation with short, structured cycles of planning, action and review. Teams use fixed rhythms (sprints, retrospectives) to keep experimentation bounded and continuously informed by feedback, so that small adjustments in one cycle can inform wider changes in subsequent ones.

The spread of ideas and behaviours depends on network connectivity and influence. If both are too weak, innovations struggle to take off; if too strong, communities become prone to panics, fads or cascades of misinformation. Once enough people cross a personal threshold of adoption, their influence can create a chain reaction in which uptake accelerates through the network.

Scientific communities institutionalise both conservatism (peer review, replication, standards of evidence) and openness (novel hypotheses, new methods). Over‑rigid orthodoxy and unconstrained speculation are opposite failures of a dynamically symmetric epistemic practice, and shifts in norms or incentives can gradually spread, reshaping what counts as acceptable inquiry.