Theosophy

In its broadest sense, theosophy could be described as "any religiophilosophical system purporting to furnish knowledge of God, and of the universe in relation to God, by means of direct mystical intuition, philosophical inquiry, or both." ("Theosophy", in Encarta Encyclopedia)
As such parts of Hinduism, and in particular several ideas of the Upanishads, the I Ching and the Tao Teh Ching, Neo-Platonism, Gnosticism, some Arab philosophies, as well as the cabala all contain theosophical elements.

More specifically, however, the term is most often used for the Theosophical Society that was founded by Madame Blavatsky.

Some core ideas or central themes are:

• The belief that both matter and spirit are emanations of God, and that by divine law, there are cycles in which spirit always descends into matter, and matter ascends back into spirit.
• The belief that all souls are essentially equal but have reached different levels of development, and that the more advanced souls function as guardians of the less advanced souls. Ascended Masters are advanced souls that have become immortal and assist the less advanced souls.
• Man has a higher and a lower nature. In order to return to the divine, the higher nature has to be purified, which happens through a series of incarnations. (This belief of the dual nature of man was already found in Orphism, the Greek cult that believed that the body of man was made of the ashes of the Titans, but his soul comes from the heart of Dionysos, son of Zeus).