Reference

Mental models

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A mental model is a way of looking that makes some things easier to see. Every one here comes with a prompt to try it on your own situation, and — just as important — where it misleads.

Reasoning

First principles — Reasoning up from what must be true, rather than across from how it is currently done.
Inversion — Approaching a goal by asking how you would guarantee the opposite.
Falsifiability — A claim worth holding is one that some observation could contradict.
Occam’s razor — Between explanations that fit equally well, prefer the one requiring fewer assumptions.
Hanlon’s razor — Do not attribute to malice what is adequately explained by pressure, confusion or not noticing.
The map is not the territory — Every model, metric and description is a simplification, and leaves something out on purpose.
Second-order thinking — Following consequences past the one you intended.

Deciding

Opportunity cost — The real cost of a choice is the best thing you did not do with the same time or money.
Reversible and irreversible — How much deliberation a decision deserves depends mostly on what undoing it would cost.
Margin of safety — Leaving room between your estimate and the point of failure, because estimates are wrong.
Circle of competence — Knowing the edge of what you actually understand, and behaving differently outside it.
Premortem — Imagining a failure has already happened so the reasons become sayable.
Sunk cost — What has already been spent cannot be recovered by continuing, so it should not enter the decision.

Systems

Feedback loops — A loop is where an effect returns to change its own cause. Reinforcing loops amplify; balancing loops resist.
The constraint — One point limits the throughput of the whole. Improving anything else changes nothing measurable.
Incentives — People respond to what their position rewards, which explains behaviour far better than character does.
Goodhart’s law — When a measure becomes a target, it stops being a good measure.
Compounding — Small repeated effects multiply rather than add, so time matters more than size.
Emergence — Simple rules followed by many people produce behaviour that is in none of the rules.
Parkinson’s law — Work expands to fill the time available for it.

Where thinking goes wrong

Confirmation bias — Searching for and weighting information that agrees with what you already think. It feels like research.
Survivorship bias — Drawing lessons from the visible successes, because the failures are not there to be counted.
Regression to the mean — Extreme results tend to be followed by more ordinary ones, with no cause required.
Anchoring — The first number mentioned shapes every judgement after it, even when it is known to be arbitrary.
Availability — Judging how likely something is by how easily an example comes to mind.
Self-justification — After acting, the mind supplies reasons that make the action right — automatically, and it feels like reasoning.
The neat story — Building a coherent explanation after the fact that makes an unpredictable event look inevitable.

Numbers & chance

Base rates — How common something is in general, before you consider the specific case in front of you.
Thinking in ranges — Describing an uncertain outcome as a set of possibilities with rough weights, rather than one prediction.
Bayesian updating — Moving a belief a proportionate amount as evidence arrives, instead of flipping or ignoring.
Correlation is not causation — Two things moving together does not tell you which caused which, or whether something else caused both.
Small numbers lie — Extreme results appear easily in small samples, which is why the best and worst are so often the smallest groups.

People

Positions and interests — A position is what someone demands. An interest is what that demand serves. Positions conflict far more than interests do.
Intent and impact — People judge themselves by what they meant and others by what happened. Both sides do it simultaneously.
Steelmanning — Stating the opposing case so well its own advocates would accept your version.
Circle of influence — The gap between what concerns you and what you can actually affect.
Position, not personality — Where someone sits in a structure shapes what they see and what pressures them, often more than who they are.