Sherlock Holmes and Spiritualism - two sides of a coin?

A friend recently lent me a book I'd never heard of before: The Edge of the Unknown' by Sir Arthur Conan Doyle. Published in 1930, the year of his death, it's presumably the last book Doyle ever wrote and it deals, as does much of his later work, with the subject of Spiritualism. It contains fifteen short, anecdotal essays, each dealing with a different example of psychic activity; what comes across most strongly is Doyle's passionate belief that the 'psychic science' of Spiritualism is a revelation especially suited to the 'modern age' (ie the early twentieth century – there is much comparison of table-rapping and mediumistic communication with telegraphy and radio reception), which is destined to bring increasing spiritual enlightenment to the human race. 'Fancy a new spiritual departure in a frame-house in an American Hamlet!' he says of the notorious 'Hydesville Rappings' that started the whole movement off in 1848– 'Yes, and fancy a previous one in a camel-driver's tent in Arabia, and before that the greatest of all in a carpenter's shop in Judea! Exaltavit humiles!' The comparison is bold and obvious, and the Spiritualist evangelism which characterised Doyle's later years, born of the heightened public profile which the movement enjoyed following the tragedy of the First World War, earned him much ridicule and detraction - though unlike other high-profile champions of the cause, he managed to keep both livelihood and reputation in tact.
Present day reactions to this side of Doyle's life and work could well be summed up in the words of his contemporary, the psychic investigator Harry Price: 'Poor, dear, lovable, credulous Doyle!' His championing of the bogus Cottingley Fairies photographs is always quoted, as is his defence of the disgraced 'spirit photographer' William Hope – followed, as often as not, by the interesting question, 'What would Sherlock Holmes have made of all this?'
The implication is, of course, that Doyle's most famous creation would most vehemently have disapproved. The quote from 'The Sussex Vampire' – 'This agency stands flat-footed upon the ground, and there it must remain. The world is big enough for us. No ghosts need apply!' – is often referenced, as is Holmes' reliance, in the face of Watson's marriage, upon 'that true, cold reason which I place above all things'. It's certainly hard to imagine Sherlock Holmes having any sympathy with the 'psychic science' which so fascinated his creator; but why are we asking the question at all? Why does it matter so much to us what a fictional character may or may not have thought of his author's beliefs?
Doyle's interest in psychic phenomena was actually in evidence while he was writing the Canon - he was experimenting with mesmerism and telepathy during the 1880s, and became a member of the Society for Psychical Research in 1893. Sherlock Holmes and the Occult were therefore occupying his mind at the same time, and should be seen as two sides of the same coin rather than as mutually exclusive preoccupations. I would even go so far as to argue (without implying any endorsement of Spiritualism as a belief system) that Holmes himself can be seen as a powerful psychic projection. Witness how many people during the last century believed the great detective to have been a real person; witness how many actors playing the role have spoken of being 'taken over' by Holmes to a disconcerting degree, and of having to struggle to retain their personal identity; witness how much sway Holmes and Watson still hold over the hearts, minds, and literary outpourings of devoted fans, how many societies and online publications still play the game that they are real, historical figures, how many shrines associated with their legend attract hordes of pilgrims, or are erected in their honour in private houses! Sherlock Holmes is a powerful entity in his own right, independent of his creator – and for all Doyle's protestations that he personally was not psychic or clairvoyant, he was undoubtedly the medium through which this entity was made manifest to the world. As we all know, he became uncomfortable under his control, and tried unsuccessfully to kill him off; but Holmes and Watson had already entered our collective psyche, and they weren't, and aren't, going anywhere.
So maybe the answer to the question 'What would Sherlock Holmes have made of all this?' isn't quite so obvious after all ...