MENTAL MODEL · M9272

Method of Difference

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Updated 2026-08-22

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INTRODUCTION

English translation pending.

CORE DEFINITION

The method of difference, one of Mill's five methods, says that if a phenomenon occurs in one situation and not in another, and the situations differ in only one factor, that factor is the cause or the effect. Its model is to control the variables and lock the causal link: by comparing two cases that change exactly one thing, the confounds are excluded and the causal relation can actually be established.

SCAFFOLDING EFFECT

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- Set the two cases: pick a present case and an absent case that are otherwise comparable. - Isolate the one difference: rule out everything the two cases share. - Verify the factor: test it directly rather than concluding from the observation.

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A cause is a difference-maker, and the factors held in common between the two cases cannot explain a difference in outcome, since they were present in both. Whatever remains after removing the shared conditions is the only candidate, which is why the comparison's validity depends entirely on the cases being truly alike except for one thing.

MINIMUM ACTION

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Practice this model in one real situation:

Select the case where the phenomenon appears and one where it does not. 2. Enumerate all the conditions shared by both of the cases. 3. Identify the single factor that differs between them. 4. Test that one factor in a controlled comparison. 5. Rule out coincidence and any hidden third variable.

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zh.wikipedia.orghttps://zh.wikipedia.org/wiki/%E9%80%BB%E8%BE%91%E4%BD%93%E7%B3%BBZH · Explicit
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