The Cum Hoc Ergo Propter Hoc Fallacy
Assumes that because two things occur together, one causes the other.
- •Definition: Assumes that because two things occur together, one causes the other.
- •Impact: Cum Hoc Ergo Propter Hoc distorts reasoning by Correlation alone doesn’t establish direction or causality; hidden factors can drive both variables.
- •Identify: Look for patterns like Observe A and B occur together.
What is the Cum Hoc Ergo Propter Hoc fallacy?
Simultaneous correlation is treated as causation without considering hidden variables, coincidence, or bidirectional effects.
People lean on this pattern because Co-occurrence is salient and tempting to explain quickly.
- 1Observe A and B occur together.
- 2Conclude A causes B (or B causes A) because of co-occurrence.
- 3Ignore confounders or testing causality.
Why the Cum Hoc Ergo Propter Hoc fallacy matters
This fallacy distorts reasoning by Correlation alone doesn’t establish direction or causality; hidden factors can drive both variables.. It often shows up in contexts like Data analysis, Health claims, Business metrics, where quick takes and ambiguity can hide weak arguments.
Examples of Cum Hoc Ergo Propter Hoc in Everyday Life
A health trend links diet and disease across regions and concludes causation without controlling for lifestyle, genetics, or environment.
Why it is fallacious
Correlation alone doesn’t establish direction or causality; hidden factors can drive both variables.
Why people use it
Co-occurrence is salient and tempting to explain quickly.
Recognition
- Causal claim rests solely on simultaneous movement.
- Confounders are unaddressed.
- No experimental or longitudinal evidence is offered.
Response
- Ask for controls and tests that separate variables.
- Propose confounders that could drive both.
- Distinguish correlation from causal inference methods.
- “Cum Hoc Ergo Propter Hoc” style claim: Assumes that because two things occur together, one causes the other.
- Watch for phrasing that skips evidence, e.g. "Assumes that because two things occur together, one causes the other"
- Pattern hint: Observe A and B occur together.
Ask for controls and tests that separate variables.
Cum Hoc Ergo Propter Hoc is often mistaken for False Cause, but the patterns differ. Compare the steps above to see why this fallacy misleads in its own way.
Close variations that are easy to confuse with Cum Hoc Ergo Propter Hoc.
Frequently Asked Questions
Cum Hoc Ergo Propter Hoc signals a weak reasoning pattern. Even if the conclusion is true, the path to it is unreliable and should be rebuilt with sound support.
Cum Hoc Ergo Propter Hoc follows the pattern listed here, while False Cause fails in a different way. Looking at the pattern helps choose the right diagnosis.
You will find it in everyday debates, opinion columns, marketing claims, and quick social posts—anywhere speed or emotion encourages shortcuts.
It can feel persuasive, but it remains logically weak. A careful version should replace the fallacious step with evidence or valid structure.