Carl Gustav Jung was one of the great early founders of the field of Psychiatry.  During his life, many of those he worked with, and others in the intellectual community, were puzzled by his involvement in things considered esoteric, mystical or even magical.  It was clear that some of what Jung taught, were things well known to ancient and some modern mystery schools.  This involvement is such things made the scientific oriented a little uncomfortable because they considered such thing to be very unscientific.
    In truth, Jung's involvement with Gnosticism and Mysticism was very scientifically appropriate.  Gnosticism and Mysticism actually takes a scientific approach to discovering truth.  The difference between Gnostic studies and the more materially oriented sciences is that gnostics and mystics are studying matters of spirit and the spiritual worlds (heaven, if you prefer) and Gnostics and Mystics recognize that, since spiritual worlds are very different from material worlds, the methods of studying them must be very different from the methods used to study the physical world.  Jung also recognized that for people to be mentally and spiritually healthy, they had to look inside and study themselves as much as they studied their external world and that also has been a teaching of Gnostic and Mystic schools for thousands of years.