"It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth"
About this Quote
Sherlock Holmes distills a method: remove what cannot be, and accept what remains, even if it strains credulity. The logic is austere and bracing. If competing explanations are tested against evidence and shown to be impossible, the survivor wins by default, not because it feels likely but because likelihood becomes irrelevant when all alternatives are ruled out. It is a creed of disciplined elimination.
The line first resonates in The Sign of the Four (1890), as Holmes instructs Watson in the habits of a mind trained to sift facts from surmise. Doyle, a physician steeped in late Victorian science, builds Holmes as a champion of observation and inference at a time when forensics and positivist thinking were remaking the investigation of crime. Across the stories, the maxim recurs as both method and drama: in The Adventure of the Speckled Band, a venomous snake through a ventilator seems outlandish until every more plausible route is barred by evidence; in The Hound of the Baskervilles, supernatural speculation is discarded, so an elaborate, all-too-human scheme remains.
Although often described as deduction, the strategy is closer to abduction and Bayesian reasoning. If the likelihood of the data given each hypothesis is zero except for one, then the remaining hypothesis, however low its prior plausibility, becomes certain under the model. But that certainty is only as good as the claim that the others are truly impossible. The method demands rigorous knowledge, scrupulous testing, and vigilance against hidden assumptions. Declaring a scenario impossible too quickly turns method into dogma.
Doyle thus champions rational courage: the willingness to accept an uncomfortable truth once the evidence has fenced off every other path. The maxim is not a license for wild conjecture; it is a call for exacting skepticism paired with intellectual humility. When properly practiced, it turns improbable into inevitable, not by intuition, but by the steady pressure of fact.
The line first resonates in The Sign of the Four (1890), as Holmes instructs Watson in the habits of a mind trained to sift facts from surmise. Doyle, a physician steeped in late Victorian science, builds Holmes as a champion of observation and inference at a time when forensics and positivist thinking were remaking the investigation of crime. Across the stories, the maxim recurs as both method and drama: in The Adventure of the Speckled Band, a venomous snake through a ventilator seems outlandish until every more plausible route is barred by evidence; in The Hound of the Baskervilles, supernatural speculation is discarded, so an elaborate, all-too-human scheme remains.
Although often described as deduction, the strategy is closer to abduction and Bayesian reasoning. If the likelihood of the data given each hypothesis is zero except for one, then the remaining hypothesis, however low its prior plausibility, becomes certain under the model. But that certainty is only as good as the claim that the others are truly impossible. The method demands rigorous knowledge, scrupulous testing, and vigilance against hidden assumptions. Declaring a scenario impossible too quickly turns method into dogma.
Doyle thus champions rational courage: the willingness to accept an uncomfortable truth once the evidence has fenced off every other path. The maxim is not a license for wild conjecture; it is a call for exacting skepticism paired with intellectual humility. When properly practiced, it turns improbable into inevitable, not by intuition, but by the steady pressure of fact.
Quote Details
| Topic | Reason & Logic |
|---|---|
| Source | Arthur Conan Doyle, The Sign of the Four (1890) — line spoken by Sherlock Holmes; standard canonical source for the maxim "When you have excluded the impossible..." |
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