The December 23, 2010, Huffington Post has an interesting overview of the philosophical current that Mme. Blavatsky was part of. The writer, Kingsley Dennis, notes in “An Age of Radical Seeking (Part One)”:
The modern world has witnessed a different type of consciousness emerging over the past 150 years, a post-Industrial Revolution cognitive mind. New technological innovations that helped to alter our perceptions of the dimensions of space and time in the world began to birth a psychological consciousness; a consciousness that wanted to look beyond the borders and horizons of the physical frontier. The end of the 19th century was also a significant period in the rise of spiritualism and mediums, general interest in esoteric matters, and the public emergence of occult movements.
Around the same time as the interest in spiritualism was peaking, the Theosophy Society was established in New York City by Helena Blavatsky, Henry Olcott, and William Judge in 1875. Theosophy heralded a revival in western occultism and in perennial wisdom. It was also a forerunner to later movements that sought to bring eastern teachings and traditions to a western audience. Theosophy has had a large impact upon western mysticism as it brought forth many personages who later found their own individual channels for teaching, most notably Annie Besant, Alice Bailey, Krishnamurti, and Rudolf Steiner (who went on to establish the Anthroposophical Society). By the end of the 19th century, spirits were well and truly out of the closet.
The rest of the piece can be read here.