What is the "post hoc ergo propter hoc" fallacy, and how does it relate to confusing cause and effect?
Post hoc = "it happened after, so it happened because of" — mistaking sequence for causation, one version of the broader error of confusing correlation with cause.
Post hoc ergo propter hoc (Latin, "after this, therefore because of this") infers that because event B followed event A, A must have caused B. But temporal order alone isn't causation: "I wore my lucky socks and we won, so the socks won the game." The two events may be coincidental, or both driven by some third factor.
It's a special case of confusing cause and effect — a family of causal errors that also includes reversing the arrow (B actually causes A) and overlooking a common cause that produces both. The underlying lesson is the classic one: correlation is not causation. Two things moving together, or one following the other, is a reason to investigate a causal link — never proof of one.
Tip: To test a "post hoc" claim, ask three questions: Could it be coincidence? Could the arrow point the other way? Could something else be causing both? If any answer is "maybe," the causal claim hasn't been earned.
Go deeper:
Post hoc ergo propter hoc — Wikipedia — the false-cause fallacy behind "correlation is not causation."