Here's a 1927 newsreel video of Sir Arthur Conan Doyle speaking about the origins of Sherlock Holmes and about his belief in spiritualism and psychic matters. A great historical document.
Note that when he speaks about Holmes, Doyle refers to "his rather stupid friend, Watson." Does this mean that Doyle supports the Nigel Brucean Watson (as do many readers) over a more thoughtful Watson (as do many readers)? Hmmm.
His views of the supernatural were heartfelt and sincere -- and perhaps magnified by the death of his son. Doyle was a brilliant man and one who was passionate about justice; even such a man could be flummoxed by his bugaboos. Remember that, at the same time he prosletyzing spiritualism, he was also firmly convinced that two little girls had actually photographed fairies.
At least he was on the right side in the Oscar Slater and George Edalji matters.
For those sympathetic the Doyle's views on spiritualism, I refer you to two books by one Ivan Cook: The Return of Arthur Conan Doyle (1956) and Arthur Conan Doyle's Book of the Beyond (1975) -- both books purportedly channeled/communicated/narrated by long-dead Doyle to psychic Cook.
Todd Mason at Sweet Freedom have all the links to more of today's Overlooked Videos.