The 2nd edition of "Advanced Dungeons & Dragons" attempted to streamline what had become a hodgepodge of rules that only applied in specific cases in 1st edition. As such, it sought to simplify the rules and straighten out contradictions. Character classes were divided into four groups or "metaclasses": Warrior, Wizard, Priest, and Rogue. Each of these groups had a "base" class which only required at least a 9 in the "prime requisite" statistic in Fighter, Mage, Cleric, and Thief; these were intended to be playable in any setting. The "Player's Handbook" went on to say that "all of the other classes are optional." Each group of classes had the same hit dice (determining hit point growth), THAC0 progression, and saving throw table. 2nd edition maintained minimums in certain statistics to qualify for some classes, but removed many of the other restrictions such as one extremely low statistic forcing a character into a specific class.