Rationality is the art of thinking in ways that result in accurate beliefs and good decisions. It is the primary topic of LessWrong.

Rationality is not only about avoiding the vices of self-deception and obfuscation (the failure to communicate clearly), but also about the virtue of curiosity, seeing the world more clearly than before, and achieving things previously unreachable to you. The study of rationality on LessWrong includes a theoretical understanding of ideal cognitive algorithms, as well as building a practice that uses these idealized algorithms to inform heuristics, habits, and techniques, to successfully reason and make decisions in the real world.

Topics covered in rationality include (but are not limited to): normative and theoretical explorations of ideal reasoning; the capabilities and limitations of our brain, mind and psychology; applied advice such as introspection techniques and how to achieve truth collaboratively; practical techniques and methodologies for figuring out what’s true ranging from rough quantitative modeling to full research guides.

Note that content about how the world is can be found under World Modeling, and practical advice about how to change the world is categorized under World Optimization or Practical.

Theory / Concepts

Anticipated Experiences
Aumann's Agreement Theorem
Bayes Theorem
Bounded Rationality
Conservation of Expected
Contrarianism
Decision Theory
Epistemology
Game Theory
Gears-Level
Hansonian Pre-Rationality
Law-Thinking
Map and Territory
Newcomb's Problem
Occam's razor
Robust Agents
Solomonoff Induction
Truth, Semantics, & Meaning
Utility Functions

Applied Topics

Alief
Betting
Cached Thoughts
Calibration
Dark Arts
Empiricism
Epistemic Modesty
Forecasting & Prediction
Group Rationality
Identity
Inside/Outside View
Introspection
Intuition
Practice & Philosophy of Science
Scholarship & Learning
Taking Ideas Seriously
Value of Information

Failure Modes

Affect Heuristic
Bucket Errors
Compartmentalization
Confirmation Bias
Fallacies
Goodhart’s Law
Groupthink
Heuristics and Biases
Mind Projection Fallacy
Motivated Reasoning
Pica
Pitfalls of Rationality
Rationalization
Self-Deception
Sunk-Cost Fallacy

Communication

Common Knowledge
Conversation
Decoupling vs Contextualizing
Disagreement
Distillation & Pedagogy
Double-Crux
Good Explanations (Advice)
Ideological Turing Tests
Inferential Distance
Information Cascades
Memetic Immune System
Philos

...

Games (posts describing)