Rule 1.01

Rule 1.01 
Baseball is a game between two teams of nine players each, under direction of a manager, played on an enclosed field in accordance with these rules, under jurisdiction of one or more umpires.


DISCUSSION
A baseball team playing under OBR must start a game and continue to play throughout the game with no less than nine players. [cf. Rule 4.17]

HISTORY
The Milwaukee Sentinel reports that in 1961 a revision to Rule 1.01 was proposed in conjunction with a new designated hitter rule. This revision was not adopted. It would have read:

"Baseball is a game between two teams of nine players, plus an optional batter per team to bat for the pitcher, with adequate substitutes, under the direction of a manager, played in accordance with these rules, and under jurisdiction of an umpire or umpires on an enclosed field."

In June of 1988, the California Angels played the Milwaukee Brewers and started the game with eight players. Angels outfielder Devon White was in the clubhouse on the telephone. At 7:05 p.m. Angels starting pitcher Mike Witt threw a strike to Milwaukee's Jim Gantner. Then White came sprinting out of the dugout to his position in center field. The umpires nullified the strike and restarted the game.
http://articles.latimes.com/1988-06-26/sports/sp-8197_1_time-white

RULES REFERENCES
Rule 2.00 MANAGER
Rule 4.03
Rule 4.17
Rule 9.01

AMBIGUITIES
The advent of the designated hitter rule allows for a team to play ten players.

"Enclosed field" is not defined.