Ultimate has traditionally relied upon a spirit of sportsmanship which places the responsibility for fair play on the player himself. Highly competitive play is encouraged, but never at the expense of the bond of mutual respect between players, adherence to the agreed-upon rules of the game, or the basic joy of play. Protection of these vital elements serves to eliminate adverse conduct from the Ultimate field. Such actions as taunting of opposing players, dangerous aggression, intentional fouling, or other 'win at all costs' behavior are contrary to the Spirit of the Game and must be avoided by all players.
Spirit of the Game sets Ultimate apart from other competitive team sports. For over 30 years, Ultimate has flourished, reaching a highly competitive level, without the use of referees. In Ultimate, the honor system works. Sure, human nature rears its ugly head from time to time - just as in any sport, just as in life. Yet, one of the many beauties of Ultimate is how, even amid the most difficult of situations, utmost graciousness is allowed to meet that challenge head on. Through this balance, Ultimate players are free to demonstrate the most honorable and the most joyous sides of human nature in sport.
Most Ultimate players care deeply about Spirit of the Game. The organizational challenge for the UPA is to foster an environment where the challenge does not become,"to see what I can get away with". Rather than dictate what Spirit of the Game is or should be, it is up to each player to do so for him or herself within the context of the teams he or she plays with and against.
Cited from the Ultimate Players Association website.