Ignoring a Common Cause
Assuming that correlations within data show that one variable causes another, and ignoring a possible underlying variable that is responsible for variables to correlate.
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Origin
The fallacy belongs to the family of questionable cause errors, a category whose Latin ancestor — cum hoc ergo propter hoc ("with this, therefore because of this") — has roots in classical logic. Formal cataloguing of causal fallacies accelerated in the 20th century; Morris Cohen and Ernest Nagel helped systematize informal fallacies in their 1934 work An Introduction to Logic and Scientific Method. The specific label "ignoring a common cause" emerged from later taxonomies in informal logic and critical thinking pedagogy.
Updated February 22, 2026