The novelist Russell Hoban says somewhere or other that ideas exist independently of people. At a certain time, an idea makes itself known to someone, but the idea has always existed and doesn't belong to anyone.
In Pan Lives, one of his extraordinary essays in 'The Moment under the Moment' (the title alone justifies the book's existence), he quotes the beginning of St John's Gospel: 'In the beginning was the word, and the word was with God, and the word was God.' He continues "I think that idea is in us independently of Christianity; I think it's simply in us and inexplicable." In another essay - which he cautiously titles with a spoonerism, Blighter's Rock - he expresses another idea which I think will always be with us for as long as there are human beings (possibly not long). He says "I think that mind is a consciousness not confined to the individual brain but shared by all of us; the brain is the organ that limits that consciousness so that we can carry on the business of every day in the consensual state we call reality. I think much, if not most, of the brain's function is repressive, holding back the accumulated contents of the mind as a dam holds back water ... If the dam ever broke we should drown in the vast chaotic roar of a flood that would sweep away our limited-reality consensus like a chicken coop."
I don't know if Blake expresses this idea directly, but something like it lies behind lines like "How do you know but ev'ry bird that cuts the airy way, / Is an immense world of delight, clos'd by your senses five?" (from Marriage of Heaven and Hell). August Strindberg, the great Swedish playwright, says something very reminiscent of Hoban in A Dream Play:
Poet: [...] what did you suffer from most down here [as a human being]?
Daughter: From - existing: to feel my sight made weak by an eye, my hearing dulled by an ear, and my thought, my bright aerial thought bound in the fatty labyrinth of a brain. You must have seen a brain ... such crooked paths, such secret ways ...
They suggest that we see the world the way we do out of habit. The surrealist painter de Chirico agreed. He asserted that madness is inherent in all great art, because it dislocates our habitual way of seeing.
That consciousness is universal, and that the brain restricts consciousness to manageable proportions seems just as plausible to me as the more common idea, that the brain in some mysterious way generates consciousness.