Initiation is a concept in Theosophy that there are nine levels of spiritual development that beings who live on Earth can progress upward through. Within these levels, there are four basic levels of spiritual development that human beings on Earth progress through as they reincarnate, although evil acts may cause bad karma which may cause one to temporarily regress. It is believed that when souls have advanced to the fourth level of initiation, they have reached enlightenment and have no further need to reincarnate. At the fifth level of initiation and beyond, souls have the opportunity to become members of the Spiritual Hierarchy. This concept was developed by both C. W. Leadbeater and Alice A. Bailey beginning in the 1920s.