If you want to understand Dogen’s philosophy you have to accept that there are many real things and phenomena in this universe that we human beings are simply not equipped to perceive, but that these things and phenomena are not parts of some mystical other realm. They’re part of our concrete reality. These days we grow up learning about infrared and ultraviolet light. So we know that there are forms of light that we can’t see. We know about the subconscious. So we know that there are realms of the mind we cannot consciously access. These are commonplace ideas. Just because we can’t normally perceive these things, we don’t think of them as supernatural the way people in Dogen’s times tended to conceive of things they could not perceive directly. So when we read Dogen we’re already prepared for much of what he wrote about in ways that his contemporaries were not.