There are in fact three features which belong to a mystery … [i]n the first place, on being confronted with a mystery we are conscious that the small central area of which we have a relatively clear vision shades off into a vast background which is obscure and as yet unpenetrated. Secondly, we find, as we attempt to penetrate this background … that the range and clarity of our vision progressively increase but at the same time the background which is obscure and unpenetrated is seen to be far greater