Probability theory really got going in 1654 with a famous correspondence between the two famous mathematicians Blaise Pascal and Pierre de Fermat, sparked off by a gambling addict by the name of Antoine Gombaud, who went by the name of the Chevalier de Mr" (although he wasn't actually a nobleman of any sort). The Chevalier de Mr had played a lot of dice games in his time and, although he didn't have a rigorous mathematical theory of how they worked, he nevertheless felt he had an intuitive "feel" for what was a good bet and what wasn't. In particular, he had done very well financially by betting at even money that he would roll at least one six in four rolls of a standard die. It's quite an easy matter to use the rules of probability to see why he was successful with this game. The odds that a single roll of a fair die yields a six is 1/6. The probability that it does not yield a six is therefore 5/6. The probability that four independent rolls produce no sixes at all is (the probability that the first roll is not a six) times (the probability that the second roll is not a six) times (the probability that the third roll is not a six) times (the probability that the fourth roll is not a six). Each of the probabilities involved in this multiplication is 5/6, so the result is (5/6)^4 which is 625/1296. But this is the probability