In blackjack, a playing strategy tells the player when to hit or stand based on the cards in front of him. A blackjack playing strategy should not be confused with a blackjack betting system, however. In blackjack, a progressive betting system is a method by which you decide how much to bet depending on whether you've just won or just lost.

Blackjack betting systems can usually be classified as "positive" or "negative." The positive betting systems are the ones in which the player raises his bet after winning, and the negative systems are the ones in which he raises his bet after losing. Either way, the betting is the key as opposed to the blackjack play itself.

In the realm of negative progressive betting systems, the Martingale Betting System is considered to be the Holy Grail. However, the d'Alembert progressive betting system is another simple negative system, which is based on the tenets of the Martingale with a few minor changes; it is also considered less draconian than Martingale. When you use the d'Alembert for blackjack betting in the online casino, you will raise your bets one unit after each losing hand, and you will lower your bet by one unit after you win.

The d'Alembert progressive betting system is named after Jean le Rond d'Alembert, a French mathematician, physicist and philosopher. One of d'Alembert's theories claims an even number of successes and failures over the course of a long series of repeated events. In casino gambling, however, there is no longevity - wins and losses cover a much shorter span of time and there is no long-term balance. Despite this "little" flaw in the theory, the d'Alembert (also known as the "Pyramid System) has become a very popular progressive betting system. It is used frequently in baccarat and roulette, but it is a popular blackjack betting system, as well.

When used in blackjack, the d'Alembert betting system requires players to raise (by one unit) their bets after each loss, while lowering (by one unit) their bets after each win. As with any progressive betting system, one must proceed with caution when using the d'Alembert; on the other hand it's considered a lot less dangerous than the Martingale system (whereby you double your bets upon losing instead of always raising them by one unit). The best aspect of the d'Alembert system is that it's easy to follow and understand.

As an example of how the d'Alembert betting system works, let's say you're playing blackjack at a blackjack table with a $2 minimum (which is considered one "unit"). You start off by betting $2. If you lose, your second bet would be $4 (two units). If you win, your next bet would be $2 (back to the original one-unit bet) but if you lose your next bet would be $6. If you win after that, you then bet $4 (you only go down one "unit," not to the original bet, in this case). All wins or losses are rewarded or punished by a one-unit decrease or increase, respectively.