Why does the rule "judge strategies, not outcomes" matter, and what bias does it counter?

Because luck separates a decision's quality from its result — a good decision can turn out badly and a bad one well — so you must evaluate the process, not the outcome (countering hindsight bias).

A decision is made before you know the result, using the information available at the time. Whether it then succeeds depends partly on chance. So:

• A well-reasoned decision can still produce a bad outcome (you played the odds correctly and got unlucky).
• A reckless decision can produce a good outcome (you got lucky).

If you grade decisions purely by how they turned out ("outcome bias"), you'll praise lucky recklessness and punish sound but unlucky judgement — and learn the wrong lessons. The fix is to ask: given what was knowable then, was this a good way to decide?

This directly counters hindsight bias, the "I knew it all along" illusion that makes a result look inevitable after the fact and tempts you to blame the decider for not foreseeing it.

Tip: Poker players live by this: a correct call that loses the hand is still a correct call. Judge the bet, not the river card.