This is an  interesting, well-illustrated introduction to Gnosticism, especially the form that developed in the first to third centuries AD, but that still influences thoughts up through today. The talk is by John Algeo, a noted National Theosophical Society lecturer.  He explains Gnostic symbols and myths,  and compares Gnosticism to Hinduism, Christianity and Theosophy.  He defines sige, pleroma, hysterema and other Gnostic concepts.  Echoes from the Gnosis by G. R. S. Mead  is the basis for this talk. Where else would you hear Mary Poppins, Joseph Campbell and Madame Blavatsky mentioned in the same lecture?