What it is
Treating an outcome as having been obvious once you know it happened.
In the wild
The crash was obvious, anyone could have seen it coming.
How to answer it
Ask what was actually written down or predicted before the event.
Causal errors
Hindsight bias
Also called Knew it all along effect
In depth
Origin and naming
Documented experimentally by psychologist Baruch Fischhoff in 1975, who showed that people told an outcome inflate how predictable it was beforehand — the 'knew-it-all-along phenomenon', also called creeping determinism. It is less an argument than a memory defect that sounds like one.
More places it shows up
After the election: 'Obviously the underdog was going to win — the signs were everywhere.' Before it: nobody circled those signs.
The startup folded and suddenly every investor says the business model was doomed from day one.
After the layoff announcement, everyone on the team 'always suspected' the company was in trouble.
The bridge collapsed and now every commenter is an engineer who saw the fatigue cracks years ago.
How to spot it
- The certainty is always backward-facing — ask what they said before, and the record is thin.
- Nobody can point to a prediction made in advance, only to 'signs' noticed afterward.
- The same people who 'knew it' are freshly surprised by the next event.