The main impulse behind the reform movement of the antebellum period was a desire to improve and perfect American society.
In the years before the reform movement arose, America went through a "Second Great Awakening" and a rise in technological and scientific know-how. The increases in science and technology gave Americans the feeling that things could change for the better. The Second Great Awakening gave a moral reason for change. It was a religious movement that emphasized people's ability and need to change themselves. With this religious revival came a greater desire to change and improve the society as a whole.
Thus, the principal impulse behind this movement was a desire to create a more perfect society in the United States.