The Mahatma Letters to A.P. Sinnett

The Mahatma Letters to A.P. Sinnett is a book published in 1923 by A. Trevor Barker. (ISBN 1-55700-086-7) According to Theosophical teachings, the letters were written between 1880 and 1884 by Koot Hoomi and Morya to A. P. Sinnett. The letters were previously quoted in several theosophical books (e.g. The Occult World by Sinnett), but not published in full. The letters were important to the movement due to their discussions on the theosophical cosmos and spiritual hierarchy. From 1939, the original letters were in the possession of the British Museum but later the British Library. The book was both praised and criticized by theosophists. Dr H. N. Stokes called the book "the most authoritative work of a theosophical nature ever made accessible to the public. It is simply transcendent in its importance."

Criticism
Patterson wrote about theosophical occult phenomena, "What if these signs and wonders are proofs of something very different?... Instead of a message from beings of supernal wisdom and power, we shall have only the private thoughts of a clever but not over scrupulous woman. "

A member of the SPR and a research worker of paranormal phenomena Richard Hodgson wrote in The Age: "'I was enabled while in India to secure various Mahatma documents for my own examination, and after a minute and prolonged comparison of these with Madame Blavatsky's handwriting, I have not the slightest doubt that all the documents which I thus had the opportunity of examining were, with the exception of one, written by Madame Blavatsky. The one exception, in my opinion, was unquestionably written by Mr. Damodar, one of her confederates; it is a document which Madame Coulomb asserts she saw being prepared by Mr. Damodar when she peeped through a hole — apparently made for spying purposes — in the wooden partition separating Mr. Damodar's room from the staircase. Further inquiries concerning the 'Mahatma' writing remain to be made from professional calligraphic experts in London. I may allude, however, to some specimens of the K.H. writing furnished by Mr. Sinnett for examination; the K.H. writing possessed by Mr. Sinnett is particularly important, because it is upon this that Esoteric Buddhism, with its large claims, is confessedly founded; and Mr. Netherclift, the calligraphic expert, has confidently expressed his opinion that the K.H. documents thus coming from Mr. Sinnett were undoubtedly written by Madame Blavatsky. How far the K.H. letters received by Mr. Sinnett emanated from the brain of Madame Blavatsky, how far she was assisted in their production by confederates, how much of their substance was plagiarized from other writers, are questions which closely concern the intellectual ability of Madame Blavatsky, and which lie somewhat outside the present brief sketch.'"

Modern criticism
Leo Klejn wrote that Blavatsky's reputation was "seriously damaged after due consideration of this occult phenomena by English psychologists". A historian of esotericism K. Paul Johnson speculates that the "Masters" that Blavatsky wrote about and produced letters from were actually idealizations of people who were her mentors.