Topic summary
Third-cause fallacy
Extracted from the Wikipedia article Correlation does not imply causation.
Third factor C (the common-causal variable) causes both A and B
The third-cause fallacy (also known as ignoring a common cause or questionable cause) is a logical fallacy in which a spurious relationship is confused for causation. It asserts that X causes Y when in reality, both X and Y are caused by Z. It is a variation on the post hoc ergo propter hoc fallacy and a member of the questionable cause group of fallacies.