Post hoc ergo propter hoc
Literally, "after this, therefore because of this".
This logical fallacy represents a mistaken assertion of causality. Two events, which may have no significant causal connection, are erroneously considered to represent a cause and its effect.
- I took 2 pills
- My headache went away
- Therefore, those pills cured my headache
Those pills might be responsible, but that causality can't be determined from this argument alone. This sort of confusion about cause and effect is demonstrated by the placebo effect and is a common basis for folk remedies and many basic religious beliefs.
- I prayed that I would find my lost keys
- I found them behind the couch
- Therefore, prayer helped me find my keys
There's no evidence that demonstrates a direct causal relationship between prayer and finding lost keys. Plenty of people have found their keys without prayer and many keys remain lost despite prayer. Yet, for those individuals who willingly accept arguments based on this fallacy, each occurrence represents another data point supporting the idea that prayer produces results.