Logical fallacies

post hoc

It happened afterwards. That does not mean it happened because of.

  • “Sales rose after the redesign, so the redesign worked.”

    “What else changed that month?”

    Seasonality, a competitor folding, a press mention. Sequence isn’t cause.

Post hoc ergo propter hoc—“after this, therefore because of this.” Our pattern-matching is aggressive and does this automatically, which is why it takes deliberate effort to notice.

How to answer it: ask what else changed, and what would have happened with no intervention at all. If nobody can say, the causal claim is a guess with a timestamp.

Now go ask what else changed.