THE REFERENCE LIBRARY
A growing collection of ideas for understanding the world — and your own thinking.
Charlie Munger finds humor and reassurance in Cicero’s De Senectute. He values its emphasis on lifelong learning, useful work, and the comfort of remembered good actions, while recognizing that health, poverty, and changing circumstances can make old age difficult.
A simple exercise to track mood before and after a planned activity, using a 1-10 scale, to observe changes and inform behavioral choices.
Erikson describes Blue decision-makers as preferring precise figures and detailed preparation. When communicating with someone who expresses that preference, give exact information where available and be clear about what remains unknown.
The representativeness heuristic is a mental shortcut where people judge the likelihood of an event by how similar it is to a stereotype, often neglecting base rates and evidence quality.
The example compares heuristics and regression for ranking homelessness rates across 50 U.S. cities using six cues. It distinguishes performance on the training data from prediction on held-out data; the supplied passage describes the comparison without reporting its results.
Bayesian reasoning, Laplace's Law, and the Copernican Principle help make predictions from limited data. Effective predictions depend on accurate prior beliefs and on understanding the underlying distribution: power-law, normal, or Erlang.
Taleb argues that models of rational choice make human behavior look more predictable than it is. He connects this critique to free will and the limits of economic forecasting.
This advanced text explores how heuristics, particularly availability, are used to estimate risks such as causes of death, emphasizing the need to understand psychological and contextual factors to predict heuristic use, accuracy, and debiasing processes.
The theory predicts that accountability to an audience with unknown views, or to audiences with conflicting views, can encourage people to anticipate objections and examine alternatives. Experiments described here found more complex private thinking when participants expected to justify their views to an unknown audience.
Studies of estimates for preexisting quantities find that people often give overly narrow credible intervals. A surprise index measures how often the true values fall outside those intervals; a rate above the intended level indicates overconfidence in the estimates.
Preference reversal occurs when different ways of eliciting a preference produce inconsistent rankings of the same options. Someone may choose one bet over another yet assign the rejected bet a higher selling price. The task can change which attributes receive the most weight.
The compatibility hypothesis explains why preferences between delayed payoffs reverse depending on the evaluation task: in pricing, the larger but longer-delayed option is often overvalued compared to choice, leading to systematic reversals that stem from scale compatibility between payoffs and pricing.
Preferential attachment describes a 'rich-get-richer' process where entities with more connections or usage are more likely to gain additional ones, generating power law distributions observed in city sizes, word frequencies, species abundance, and language adoption.
A set of questions for examining initial commitments, self-interest, suppressed dissent, and premature closure before making a decision.
Prejudicial language uses favorable or unfavorable labels to make a position seem morally required without supporting the claim. Examine the reasoning behind the label.
Premature solution bias describes proposing or defending a fix before defining the problem it is meant to solve. It can divert a discussion toward preferred answers while leaving the causes and desired outcome unclear.
A premortem asks you to imagine that a plan has failed and identify plausible reasons. Use those reasons to check assumptions and address risks before committing to the plan.
A premortem is a decision-making technique that involves imagining a project or plan has already failed and then working backward to identify potential causes, counteracting overconfidence by forcing an ego-check.
A premortem is a decision-making technique where you imagine a future in which you have failed to achieve a goal, then work backward to identify potential causes of failure. This negative visualization helps anticipate obstacles, reduce optimism bias, and improve planning and execution.
When presenting an argument or proposal, expect detailed counterquestions that test your knowledge and preparation. Failing to answer them well can damage your credibility.
Charlie Munger expands on Johnny Carson's prescriptions for guaranteed misery, adding his own rules for unhappiness including unreliability, not learning from others, giving up after setbacks, and failing to use inversion thinking.
Present bias gives an immediate reward disproportionate weight relative to a later cost or benefit. It can contribute to procrastination, comforting rationalizations, and spending decisions that conflict with a person’s longer-term plans. Borrowing itself does not establish that this bias is at work.
Present bias gives immediate rewards extra weight relative to future benefits. Hyperbolic discounting describes a related pattern: the discount rate declines as the delay grows. Specific commitments and useful defaults can help people follow through on long-term goals.
Presumed consent treats eligible people as willing organ donors unless they opt out. Thaler and Sunstein ask how much inaction reveals about a person’s wishes, especially when the default is poorly understood or hard to refuse, and examine the role families play under soft versions of the policy.
Thaler and Sunstein argue that an organ-donation default can strongly affect recorded preferences without necessarily increasing transplants. Family consultation, implementation, and donation infrastructure complicate attempts to isolate the effect of presumed-consent laws.
A heuristic for dealing with people who crave attention (e.g., 'Yellows'): deliberately ignoring them to throw them off balance by making them feel invisible.
Hayek warned that planners can overestimate their knowledge by treating a social system as if all its relevant information were available to them. Knowledge is dispersed among participants, so coordination must draw on information that a central authority may not possess.
HALT—Hungry, Angry, Lonely, Tired—is a reminder to check your condition before an important decision. If the decision can wait, address the immediate need and return to it under better conditions.
Using a Bowtie perspective, root cause analysis checks the objective, the threats, the planned safeguards, and whether those safeguards worked. Prevention, detection, and recovery measures can also be examined before a failure occurs.
The Socratic principle that true knowledge requires understanding the essential definition (Form) of a thing, not merely its observable properties. This approach prioritizes definitional clarity over empirical description and is central to Plato's theory of Forms.
Randomly distributed observations can form clusters, so clustering alone does not establish a common cause. Ellenberg connects this insight to prime numbers, which are deterministic but can be studied with probabilistic heuristics. He introduces prime factorization and prime density as background to questions about gaps between primes.
Despite being perfectly deterministic, prime numbers behave in many ways as if they were randomly distributed. This heuristic allows mathematicians to make probabilistic predictions about prime gaps, twin primes, and other patterns, which match observed data remarkably well.
Priming occurs when exposure to one stimulus affects the processing of related information, often without conscious awareness. Kahneman illustrates it with word completion and describes studies investigating links between cues, actions and emotions.
Priming is a cognitive phenomenon where exposure to one stimulus influences the response to a subsequent stimulus, making related concepts more accessible. It demonstrates spreading activation in semantic networks.
Priming refers to the process by which exposure to a stimulus influences responses to subsequent stimuli, often unconsciously. Studies demonstrate that subtle environmental cues can significantly affect behavior, judgments, and choices without our awareness.
Prince II is a project management framework for delivering change projects, emphasizing principles such as justified project continuation, clear roles, stage-based work, escalation tolerances, context adaptation, and continuous learning.
The principle of explosion (Ex Falso Quodlibet) states that from a contradiction any proposition follows, highlighting the fragility of formal logical systems. Human reasoning, however, tolerates contradiction, enabling techniques like reductio ad absurdum and the heuristic of proving a hypothesis by day and disproving it by night.
Taleb’s principle evaluates a risk as if it would be repeated at a specified frequency over the unit’s remaining lifespan. With a fixed positive independent ruin probability, cumulative ruin risk approaches 1 as the number of exposures grows without bound; a finite horizon requires its own assessment.
Delaying judgment and evaluation lets you explore the potential usefulness of ideas, even when they seem flawed or incorrect. This encourages creativity and lateral thinking.
A set of principles to improve time efficiency: set meaningful goals, break large tasks into smaller pieces, tackle unsavory tasks first, and take regular breaks to maintain productivity.
Prioritisation involves focusing resources and attention on the most critical areas to maximise impact and manage risks. It is applied across various domains including medicine, supplier management, process execution, financial controls, business continuity, and cyber risk management.
Private companies, hospitals, and universities often have excessive bureaucratic rules and sludge, similar to government agencies. This increases costs and frustrates employees, but alternative approaches like Netflix's 'spend company money as if it were your own' can reduce red tape and improve agility.
Privilege is analyzed as a hierarchy of intersecting attributes (e.g., rich, white, male), revealing a tension between the number of privilege types a person holds and their absolute societal advantage. This tension helps explain animosity between groups. Discussions of disadvantage need to account for context.
The tendency to overvalue an innovation's benefits while underestimating its limitations or risks.
Redefining confidence as a numerical probability (e.g., 73%) allows for mutual recognition of uncertainty and invites open debate, rather than asserting certainty.
Nate Silver’s election forecasts expressed uncertainty through probabilities that changed as the evidence changed. Ellenberg uses criticism of those forecasts to explain why an uncertain prediction can be informative, and why a forecaster can expect some errors without knowing which calls will be wrong.
Probabilistic thinking means considering possible outcomes, estimating their likelihoods and weighing their consequences. The theory behind it developed partly from Pascal and Fermat’s 1654 correspondence about gambling. Useful estimates make uncertainty explicit and can be revised as evidence changes.
Estimate probabilities using relevant past data, an explicit model, and the evidence available. Counts alone are not enough unless the outcomes are equally likely. When making a decision, consider both the chance of an outcome and its consequences, including losses you could not recover from. Historical frequencies and expected values are useful guides, but neither guarantees what will happen next.
Probability is a branch of mathematics that quantifies the likelihood of events, developed by Blaise Pascal and Pierre Fermat in the 17th century. It covers fundamental concepts such as independent and mutually exclusive events, and methods for calculating probabilities including logical, relative frequency, and subjective approaches.
Probability expresses uncertainty about outcomes. Jones emphasizes checking the assumptions behind estimates, combining probabilities with the appropriate rules, and communicating numerical judgments without implying more precision than the evidence supports.
Probability gives uncertainty a numerical form. Bayesian and frequentist methods offer different ways to interpret and estimate it; useful results depend on the data, assumptions, and question being asked. Marginal, joint, and conditional probabilities answer different questions about possible outcomes.
Words such as 'likely' and 'slim chance' can mean different things to different readers. Jones reports interpretations ranging from 1% to 85% across different expressions. Clarify the intended probability and its basis; his preference is to use numbers during analysis and avoid unsupported precision in reports.
The concept critiques the assumption that probabilities of future events can be measured like temperature. It argues that probabilities are often incomputable, especially for rare events with large consequences, and that people do not converge to the same probabilities due to psychological biases and the nature of statistical distributions. This is linked to the concept of Black Swan events and the Fourth Quadrant.
This excerpt introduces Jones’s probability-tree discussion by explaining why intuitive judgments and vague probability language can mislead. It includes a rain-forecast example, but not the promised exercise or instructions for constructing the tree.
A probability tree analysis is a step-by-step method for mapping out all possible scenarios in a decision problem, assigning probabilities, and calculating conditional probabilities to answer questions about events and decisions.
Expected value combines the probabilities and sizes of outcomes. A high chance of being right can still produce an expected loss when the occasional downside is large.
People often confuse probability with expected value, failing to account for the magnitude of outcomes. This leads to underestimating rare but severe consequences, especially in asymmetric environments like finance.
The long-running debate between frequentist and Bayesian statisticians over how to define probability—objectively as long-run frequencies or subjectively as degree of belief—has become an identity battle with strong emotions and even songs.
Taleb connects probabilistic thinking with skepticism and willingness to revise an opinion. He presents Cicero’s openness to changing his mind as a strength rather than a demand for consistency with every past statement.
The way a problem is stated for brainstorming greatly influences the quality and range of ideas generated. Too broad a statement leads to scattered ideas, while too narrow a statement restricts creative thinking; the ideal statement is specific enough to guide but open enough to allow diverse solutions.