1654: Probability theory - The book of science

Probability theory
Odds
Betting
Commentary

Blaise Pascal, Pierre de Fermat probability

Probability theory

Pascal and Fermat corresponded
over “the problem of points,” that is,
how to fairly divide the stakes of a game
if the game were left unfinished.
They were the first to realize
that fairness depends on the number
of possible outcomes left in the game.
Fermat drew a tree of all possible outcomes,
and counted how many outcomes
led to each player winning.
Pascal showed how to calculate the number of outcomes
and introduced the notion of expected value,
the weighted average of all possible outcomes.

Odds

One’s odds are the ratio
of the probability of an event happening
to the probability of it not happening.
You might have a one in five odds
of reading this,
given that you noticed it at all.

Betting

My advice: Retire early and beat the odds.
With a lifetime annuity or traditional retirement plan,
the company should end up paying you to live longer;
however, the law of large numbers is against you
and they are banking on that. Actuarial tables say
you will die before you’re eighty-five.
Go ahead and defy them, and don’t forget
quality is as important as quantity. Defy them; live a long and happy life.
You’ll be in trouble only if everyone does it.

This correspondence between Pascal and Fermat influenced Christiaan Huygens, who published the first book on probability theory three years later. Huygens was the guy who first declared that Saturn has a ring, and who invented the pendulum clock.

Fermat was the first to evaluate the integral of general power functions, which influenced both Newton and Leibnitz in their creation of calculus.