A Renaissance gambling dispute spawned probability theory

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TLDR

  • The “problem of points” went unsolved for 150 years until Pascal and Fermat’s correspondence produced expected value, the foundation of modern risk assessment.

Key Takeaways

  • Pacioli’s 1494 proportional split and Tartaglia’s lead-relative fix both broke at edge cases; neither accounted for future possibilities.
  • Fermat solved it by enumerating all possible future coin-flip continuations; Pascal used recursive backward induction from a tied-game baseline.
  • Both methods converge: score 8-6 in a race to 10 points gives the leader exactly 81.25% of the pot ($81.25 on a $100 stake).
  • Expected value = sum of (outcome x probability) across all futures; the same calculation actuaries, portfolio analysts, and sports bettors run today.
  • Pascal’s recursive method scales where Fermat’s enumeration breaks down – 20 flips remaining means 1M+ futures to list.

Hacker News Comment Review

  • Commenters noted Luca Pacioli’s double role: he also formalized double-entry accounting, making him an unlikely founder of both modern bookkeeping and proto-probability.
  • The two-comment thread is thin on technical depth; discussion is anecdotal rather than analytical.

Notable Comments

  • @The_Blade: Links Pacioli to double-entry accounting; notes probability “has always been way behind other maths”; cites real Polymarket/Kalshi use as modern payoff.

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