Master Dogen, and the other great Zen Masters of the past, discovered [that the] friction and fear of “opposing” requires a world of separate things to “oppose” each other, while dropping away the sense of separation into some “Wholeness” removes all chance of “opposition.” One encounters a singular nature to reality, a unity, which is simultaneously this world of multiplicity. If it takes “two to tangle,” and if this world is “not just one, yet not two either” (a singular, flowing whole which is also this world of separation and multiplicty), then the world’s problems untangle even as they tangle. In fact, if there is a separate person (you or me) who experiences that there exists an apparently “outside” situation viewed as a “problem,“ the “problem” must vanish when thoughts of “viewer” and “viewed,” “inside” vs. “outside” drop away. Because the sense of “viewer” and “viewed” fall away, we might sometimes call such knowledge a “viewless view.” Likewise, our Practice involves dropping off our subjective judgments on situations as good or bad, happy or sad, problems or not problems. All is “just what it is” without judgments. We do so even as we continue to live by another perspective (simultaneously present with the “perspectiveless” beyond separation) of a life of good and bad, happy and sad, problems or not problems, you and me, and all the other separate people and things. Then, one encounters a world filled with good and bad, separate people and things, yet transcendent of the same at once.
One does this in our Zazen (Zen meditation) and all our Zen Buddhist Practice. That is where the sense of separation drops away in Wholeness, even as we live in a world of separation too. Very simple to explain really.
Of course, realizing this, getting it into our bones and letting us live this is what our Practice is about.