Millennium refers to 1,000 years. In the study of end-time doctrines (eschatology), the millennium is the period of time of Christ's rulership. The debate has been over when the millennium will take place and what form will it actually be. The terms that have arisen out of this debate are premillennialism, amillennialism, and postmillennialism. Premillennialism teaches that the millennium is yet future and that upon Christ's return He will set up His earthly kingdom. Amillennialism teaches that the millennium is a figurative period and that Christ's rule began when He first became man. Postmillennialism teaches that through the preaching of the Word of God the world will be converted and will then usher in Christ and the kingdom of God. There are good arguments for each position.