The beliefs of Spiritualism vary among groups though they share certain beliefs.
The only base belief I would like to have is of the supernatural, the belief that there is something more powerful than us. If this supernatural power influences us to do good stuff you may believe it as a god and on the contrary if it tends to do bad stuff you may term it as Dark and negative force. All religion and religious messiah seem to have fair good understanding of this basic thing and form the basis for the religion.
Though none claim to have really seen this supernatural being but have confessed have felt the presence during troubled times.