What is post hoc ergo propter hoc, and how does it relate to "correlation is not causation"?

Concluding that because B happened after A, A must have caused B — mistaking sequence (or mere correlation) for a causal link.

Latin for "after this, therefore because of this." The pattern: A occurs before B; therefore A caused B. It fails because precedence (or correlation) alone doesn't establish causation — countless things precede an event without causing it.

"I wore my lucky socks and then aced the test, so the socks caused the good grade."

Two events lining up in time (or rising together in a chart) can be coincidence, reverse causation, or both driven by a hidden common cause. Related causal fallacies:

• Confusing cause and effect — getting the direction backwards (does illness cause the fever, or the fever the illness?).
• Ignoring a common cause — A and B correlate only because a third factor C causes both (ice-cream sales and drownings both rise with summer heat).

Tip: Before claiming A→B: check the timing, rule out reverse causation, and hunt for a lurking third variable.