LogicalMANIPULATIVE

Post Hoc Ergo Propter Hoc

What it is

Assuming that because one event followed another, the first event caused the second — confusing sequence with causation.

How it works

Temporal sequence is one piece of causal evidence, but by itself proves nothing. Many things happen in sequence without causal connection. This fallacy exploits our brain's compulsive pattern-matching, which evolved to identify real causal relationships but frequently fires on coincidences.

Real-world examples

  • •"I wore my lucky shirt and we won the game, so the shirt caused the win."
  • •"Crime decreased after we elected the new mayor, so the mayor reduced crime" — ignoring other factors.
  • •"I started taking this supplement and my cold went away in a week" — colds naturally resolve in about a week.

Ethical guidelines

  • ●Claiming causation without proper evidence can lead to ineffective or harmful decisions.
  • ●Correlation studies should be clearly distinguished from causal evidence.
  • ●Marketing claims that imply causation from sequence are particularly deceptive.

How to defend against it

  • ►Always ask: "Could there be another explanation for why B followed A?"
  • ►Look for controlled studies rather than accepting anecdotal sequence as causation.
  • ►Remember that coincidences are far more common than we intuitively expect.

From the Defense Playbook

The Toulmin Checkminutes

Test any single argument by asking Toulmin's six questions of it: what is the claim, what are the grounds, what warrant connects them, what backs the warrant, how strongly is the claim qualified, and under what conditions would it fail?

Fallacy Audit of Your Own Caseminutes

Before you publish, present, or press an argument, go through it as a hostile reader would, looking for the fallacies and statistical shortcuts you would attack in an opponent, and fix or cut what you find.

Every playbook entry states how strong its evidence is and when not to use it. Browse the full playbook.

References

  1. Copi, I. M., Cohen, C., & McMahon, K. (2014). Introduction to Logic (14th ed.). Pearson
    Textbook treatment of post hoc ergo propter hoc as a form of the false-cause fallacy: temporal succession alone is taken as proof of causation — the entry's definition.
  2. Michotte, A. (1963). The Perception of Causality. Methuen
    Classic experiments showing that observers perceive causation directly from the timing of successive events, even when none exists — the entry's claim that our pattern-matching fires automatically on mere sequence.
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