path. This knowledge transfer is sometimes said to occur through Maitreya occasionally manifesting or incarnating in the physical realm, then assuming the role of World Teacher of Mankind. The Theosophical concept of Maitreya has many similarities to the earlier Maitreya doctrine in Buddhism. However, they differ in important aspects, and developed differently. The Theosophical Maitreya has been assimilated or appropriated by a variety of quasi-theosophical and non-theosophical New Age and Esoteric groups and movements. These have added, and advanced, their own interpretations and commentary on the subject. Development of the concept The first mention of Maitreya in a Theosophical context occurs in the 1883 work Esoteric Buddhism by Alfred Percy Sinnett (1840–1921), an early Theosophical writer. The concepts described by Sinnett were amended, elaborated on, and greatly expanded in The Secret Doctrine, a book originally published 1888. The work was the magnum opus of Helena Blavatsky, one of the physical founders of the Theosophical Society and of contemporary Theosophy. In it, the messianic Maitreya is linked to both Buddhist and Hindu religious traditions. In the same work Blavatsky was to assert that there have been, and will be, multiple messianic (or messianic-like) instances in human history. These successive appearances of "emissarie of Truth" are according to the Blavatsky writings part of the unceasing oversight of Earth and of its inhabitants by a physically hidden Spiritual Hierarchy, called Masters of the Ancient Wisdom. The Theosophist, Alice Bailey, who broke with the Indian branch of the Theosophical Society, and who was heavily influenced by orthodox Christianity, started the expectation that the ""Maitreya" would actually be reborn on the earth as a physical being, fulfilling the Christian ideal of a Second Coming, rather than the New Age ideal of the Christ being reborn in the heart of each individual. Initiation 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.