Steelman
Correlation is not causation
Also called cum hoc, ergo propter hoc (“with this, therefore because of this”), cum hoc fallacy, correlation/causation fallacy, questionable cause.
Assuming that because two things occur together, one causes the other.
What it is
Concluding that one thing causes another merely because they are correlated (they rise and fall together, or appear together) without ruling out coincidence, reverse causation or a common cause.
The pattern
A and B are correlated. Therefore A causes B.
An example
“Countries that eat more chocolate have more Nobel Prize winners per person. So chocolate boosts brainpower.”
A real correlation has been reported, but wealth plausibly drives both chocolate consumption and research funding. The data can’t show chocolate is the cause.
Why it fails
A correlation has several possible explanations: A causes B, B causes A, some C causes both, or it’s chance. The correlation alone can’t tell them apart.
When it’s not a fallacy
Most lists skip this part. Calling a fair point a fallacy is a mistake too.
It can be fair when
- The correlation comes with evidence that rules out the alternatives: randomized experiments, natural experiments, a known mechanism. Correlation is evidence for causation, just not proof on its own.
Try one
A question from the app. The wrong answers are its usual look-alikes.
Football podcast. Joe: “Fun stat: the leagues that use video review draw far bigger crowds than the ones that don’t.” Dan: “There it is. People want the calls right, and they’ll pay to see it done right. Every league still holding out should take note.”
What’s the flaw?
Joe’s stat only shows that the two go together. The leagues rich enough to pay for video review may simply be the ones that already drew big crowds, for plenty of other reasons, so it doesn’t show the replays bring anyone in.
A fair reply
“The big leagues had big crowds long before video review, so how do we know it’s bringing anyone in?”
Often confused with
- Post hoc
Post hoc relies on one thing following another in time. Cum hoc relies on things occurring together.
- Ignoring a common cause
Ignoring a common cause is one specific way a correlation misleads.
- Reverse causation
Reverse causation is another specific way: the arrow points the other way.
Where the name comes from
Cum hoc, ergo propter hoc is Latin for “with this, therefore because of this”: two things show up together, so one must cause the other. Its cousin post hoc swaps “with” for “after”. A correlation is two things moving together, and “questionable cause” is the wider family of shaky claims about causes.
Sources
- Fallacies, Bradley Dowden, Internet Encyclopedia of Philosophy
In the app
Practice spotting it on arguments that sound real.
Steelman has more examples of correlation is not causation, how to answer it in a real conversation, and practice rounds that mix it with its look-alikes, so you learn the difference, not just the name. Coming soon to iPhone and Android.
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