Post hoc vs correlation
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Sequence is not a cause. Moving together is not a cause either. This library files the first mistake as post hoc. It does not file a separate correlation card.
Post hoc
Post hoc ergo propter hoc treats “after this” as “because of this.” Order in time is necessary for a cause of that kind, but it is not sufficient. Other changes may explain the result.
“After the town changed the bus timetable, the bakery’s sales fell. So the timetable caused the drop.” A new shop, the weather, or prices could explain it.
Open the cardCorrelation
This library does not file a separate card under that name. The contrast below uses the post hoc card and ordinary English, and it does not invent a second entry.
How to tell them apart
Post hoc, on the card in this library, is the jump from “this came after that” to “this was caused by that.” Order in time is the whole reason on offer.
Correlation, as this page uses the word, means two things vary together. That is a different observation. They can rise together because one causes the other, because something else moves both, or because the pairing is a coincidence. The library does not keep a second fallacy entry under the name correlation.
Do not treat the two words as synonyms. A sequence with no co-movement is post hoc if you call it a cause. A co-movement with no story about time is not yet post hoc, and it is still not yet a cause. The post hoc card’s question still helps: what, besides the order, ties the two things?
FAQ
What is Post hoc?
Post hoc ergo propter hoc treats “after this” as “because of this.” Order in time is necessary for a cause of that kind, but it is not sufficient. Other changes may explain the result.
What is Correlation?
Correlation, as this page uses the word, means two things vary together. That is a different observation. They can rise together because one causes the other, because something else moves both, or because the pairing is a coincidence. The library does not keep a second fallacy entry under the name correlation.
How do you tell Post hoc from Correlation?
Post hoc, on the card in this library, is the jump from “this came after that” to “this was caused by that.” Order in time is the whole reason on offer.