 As already explained, in ancient Japan proto-Shintō had the sketch of a basic world view and set of values, but it had lacked philosophical explanation or argumentative justification. In the early ninth century esoteric Buddhism supplied the philosophical underpinnings for what was, in effect, a quite similar view of reality as a field of interdependent, internally related events that are always in flux. Esoteric Buddhist philosophy had relegated Shintō to being a surface manifestation of what, on a deeper level, could be explained as a Buddhist reality. That is roughly how the situation stood for much of the medieval period with one notable exception.