Rule of Distributed Middle
Updated 2026-08-10
INTRODUCTION
English translation pending.
CORE DEFINITION
A rule of syllogistic logic stating that the middle term, the concept shared by the two premises, must be distributed in at least one premise, meaning that premise must refer to its entire extension. Its core proposition is that when the middle term is undistributed in both premises, each premise covers only part of it, so no necessary connection between the major and minor terms can be established and the reasoning is invalid. The qualifier is that the rule tests validity rather than truth, since true premises can still be arranged invalidly.
SCAFFOLDING EFFECT
Reduce cognitive load
- Structure writing: write out the major premise, minor premise, and conclusion in full. - Middle marking: identify the term that appears in both premises and nowhere else. - Distribution check: verify the middle term is distributed in at least one premise.
Anchor fast decisions
The middle term is what links the two premises, so the connection it establishes holds only over the portion of its extension that the premises actually cover. If neither premise covers the whole of that extension, the two premises may each be speaking about a different part of it, and the major and minor terms are never joined at all.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Fallacy_of_the_undistributed_middleverified
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