The Reasoning Guide
Fallacies break arguments; biases skew judgment. One clean, linkable page for each — what it looks like, why it goes wrong, and how to respond well.
Logical Fallacies
All 38 fallacies →Broken arguments — what they look like, why the reasoning fails, and how to respond.
Ad Hominem
Attacking the person making the argument — their character, motives, or background — instead of addressing the argument itself.
RelevanceAppeal to Authority
Treating a claim as true because an authority said so — especially outside their expertise — rather than because of the evidence.
AppealBandwagon
Arguing something is true or right because many people believe or do it.
AppealCherry Picking
Selecting only the evidence that supports your position while ignoring the evidence that contradicts it.
PresumptionFalse Dilemma
Presenting only two options when more exist, forcing a choice between extremes.
PresumptionMoving the Goalposts
Raising the standard of evidence after it's been met, so no amount of proof can ever settle the question.
AmbiguityRed Herring
Introducing an irrelevant point to divert attention from the actual issue under discussion.
RelevanceSlippery Slope
Claiming that a first step will inevitably trigger a chain of events ending in disaster, without showing each link is likely.
CausalStraw Man
Misrepresenting someone's argument to make it easier to attack — then knocking down the distorted version instead of what they actually said.
RelevanceWhataboutism
Deflecting a criticism by raising a different wrongdoing — "but what about X?" — instead of answering the point at hand.
RelevanceCognitive Biases
All 20 biases →The mind's systematic errors — every entry backed by replicated evidence.
Anchoring
The first number you encounter pulls your estimate toward it — even when that number is arbitrary, irrelevant, or obviously too high or too low.
JudgmentConfirmation Bias
The tendency to seek out, favor, and remember information that supports what you already believe — and to overlook or discount whatever cuts against it.
EvidenceFraming Effect
Deciding differently depending on whether the same option is described as a gain or a loss. The facts don't change — the wording does, and the choice follows the wording.
JudgmentFundamental Attribution Error
Explaining other people's behavior by their character while underrating the power of their situation: the driver who cut you off is a jerk, never someone rushing to a hospital.
SocialHalo Effect
Letting one appealing trait — looks, confidence, warmth, success — color everything else you believe about a person, brand, or idea. One bad trait does the same in reverse.
SocialHindsight Bias
Once you know how something turned out, it feels like you saw it coming all along — the outcome quietly rewrites how predictable the past seems.
JudgmentIllusory Truth Effect
The tendency to judge a claim as more likely true simply because you've heard it before — repetition, not evidence, does the persuading.
EvidenceSunk Cost Fallacy
Sticking with a failing course of action because of what you've already put into it — money, years, effort — even though nothing you do next can recover what's spent.
DecisionSurvivorship Bias
Judging a group by its visible successes because the failures never made it into view — when the missing cases carry the real lesson.
Evidence