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.

According to C.W. Leadbeater, Initiation is a process by which "we try to develop ourselves not that we may become great and wise, but that we may have the power and knowledge to work for humanity to the best effect."
According to Alice A. Bailey,
Initiation is the "process of undergoing an
expansion [toward higher levels] of consciousness".

It is believed by Theosophists that all souls that have reached the fourth level of initiation and evolved beyond the necessity to reincarnate that do not elect to become pratyeka buddhas and go directly into Nirvana gradually evolve upward through all of these six higher levels of consciousness over thousands or millions of years, and later over billions or trillions of years, other higher levels yet beyond.

The concept of Initiation is also recognized in the Ascended Master Teachings , a group of religions loosely based on Theosophy. In the Ascended Master Teachings, it is referred to as Ascension .

The first six initiations were named by C.W. Leadbeater and Alice A. Bailey after the six most important events in the life of Jesus .
According to Martin Euser, “Theosophy closes the gap between science and religion by positing reincarnation as a dynamic process [ unlike the concept of the eternal return ].

The first jewel concerns the doctrine of reincarnation or reembodiment. It's all a dynamic process and it's the way nature works.”