Eternal Progression is a doctrine unique to Mormonism, which teaches that men can eternally progress to the state of godhood.
Eternal Progression is taught by the LDS that the process begins as the spiritual children of God in the “preexistence” and then continues throughout life on Earth and afterward. Through obedience to God, the doctrine says, one can become a god.
“The principal purpose of the gospel of Jesus Christ and the ultimate goal of eternal progression is to receive eternal life, i.e., to become as God is. It is thoroughly understood, however, that a vast majority of the human family will never become gods, because to do so they must accept the true gospel, receive all of the ordinances-including celestial marriage-and obey all of God’s commandments faithfully to the end,” Milton Hunter, 1968.
The Brigham Young University websites says:
The concept of eternal progression is a salient feature of the gospel of Jesus Christ, readily distinguishable from traditional Christian theology. The philosophical views of the Middle Ages were basically incompatible with such a concept, and the idea of progress that emerged in the eighteenth-century Enlightenment was that of social evolution (Bury, The Idea of Progress, London, 1932). The traditional Christian view has held that those in heaven enter “a state of eternal, inactive joy. In the presence of God they would worship him and sing praises to him eternally, but nothing more” (Widtsoe, p. 142). Latter-day Saints, however, constantly seek personal and righteous improvement not only by establishing Zion in this world, but by anticipating the continuation of progression eternally.
With the heresy of eternal progression, Mormonism is quite literally the most (potentially) polytheistic religion in history.