John le Rond d’Alembert was a prominent physicist and mathematician in the 18th century, who also liked to gamble. He developed a very simple betting strategy that can be applied to any casino game, but is especially easy to use when playing roulette.
Back in 18th century Paris, John le Rond d’Alembert argued that if a fair coin was flipped twice, the second flip would be more likely to be the opposite of the first flip. In other words, if heads comes up, it is more likely that a tail must next time as variance must even itself out.
Of course, mathematicians now agree that each flip is independent and that each flip has exactly a 50% of being heads and 50% tails; the coin has no memory. But d’Alembert didn’t agree with this and devised his betting system around his beliefs.
Start out with as much or are little as you like and bet on the even money wagers on the outside of the roulette table – let’s say we’re betting $10 on even. If we win, we decrease our bet by $1 to $9 and if we lose, we increase it by $1 to $11. It’s as simple as that.
The idea is that when we hit a losing streak, we increase our bet in order to take full advantage when the roulette wheel beings to “even out”. Similarly, when we are winning we must anticipate a future run of losses and therefore expect to lose money, so we reduce our wager accordingly.
The d’Alembert system’s main strength lies within its simplicity – even a complete roulette novice should have no trouble employing this particular betting strategy. But it is also popular as it is far less volatile than some other betting systems, particularly the Martingale.
The main flaw in the d’Alembert system is the idea that the roulette wheel must eventually even out. As we now accept, this is simply untrue. There is absolutely nothing to stop a wheel producing 1,000 odd numbers in a row and so this particular roulette strategy is as susceptible to long losing runs as any.