The critiques to this view generally perceive these ideas as arising from some unconscious mentation that is going on in the brain at a sub-level, but they cannot say exactly how; and they really can't say how this mentation can often be not only complete (endowed with a full personality) but - and this important to the psychologists - far smarter than the daily personality. And, as mentioned, when this other self also has information beyond what the person should have, we have a double whammy on the materialist view.
As for me, this is preaching to the choir. Like our discussion of "over-analysis", when you experience it, you know it.
More exciting are the accounts of true geniuses of their muse. The true genius is one who not only receives the most sublime information from the hidden realm (some information 'from the depths" are unimportant or rattled fragments, such as in many dreams) but also is capable of handling such information with his duly-practiced skills. So they say, but to read what these geniuses have to say about it, one wonders; the idea of "automatism", that is, work done with little or no input from the physical person, does come to mind.
And so with that in mind, I give some quotes from or about such geniuses that I found very interesting and revealing:
From psychologist Ghiselin (1952): "There is a sense of self-surrender to an inward necessity inherent in something larger than the ego and taking precedence over the established order...Production by a process of purely conscious calculation seems never to occur...More or less of such automatism is reported by nearly ever worker who has much to say about his processes, and no creative process has been demonstrated to be wholly free from it."
From William Blake, about his famous long poem Milton: most of the work came "from immediate dictation, twelve or sometimes twenty or thirty lines at a time without premeditation and even against my will. Th time it has taken in writing was thus rendered non-existent, and an immense poem exists which seems to be the labour of a long life, all produced without labour or study...I may praise it, since I dare not pretend to be other than the secretary."
From Nietzsche: "There is an instinct for rhythmic relations which embraces an entire world of forms (length, the need for a widely extended rhythm, is almost a measure of the force of inspiration, a sort of counterpart to its pressure and tension). Everything occurs quite without volition, as if in an eruption of freedom, independence, power and divinity. The spontaneity of the images and similes is most remarkable; one loses all perception of what is imagery and simile; everything offers itself as the most immediate, exact, and simple means of expression."
Of the last, I found most interesting the idea of "rhythm" because, some where along in my writing career, I noticed for the first time that I was often tapping my foot to the inner rhythm of the book, one about which I had no previous idea. As Nietzsche said, this is a "widely extended rhythm," with some markings of musical rhythm, but different, too, and one that I had never heard of before. It is tempting to speculate on the importance of rhythm here in human history, as poetic form was formerly THE way to communicate stories. Julian Jaynes claims this is a trait of the mythopoetic mind found in the right hemisphere, exactly where "God" is found. And yet the authors of "Irreducible," in other sections, point out that the hemispheres of the brain are much more coordinated than that; and besides, one has to wonder where the "homonucleus" is that orders the right brain to produce such profound works, works made,as the materialist would have it, from the scraps and bits provided by our senses. FK