In trying to understand the writings of Dogen and of the Chinese Zen Masters, an often difficult task, it’s useful to bear in mind what they’re trying to do, and the dilemma they’re attempting to resolve.
They’re aiming to express nonduality yet they’re obliged to do that in language, which is intrinsically dualistic. They’re trying to express a wholeness which is realistic: not a wholeness dependent upon a special or disordered state of consciousness and not just conceptual either.
One of the ways that they accomplish this is that they appear to use the same word or the same phrase in two apparently dramatically different ways. For example, Dogen famously [in the Genjokoan] uses the word self [ jiko’] to mean both the “the ego” and also the “body of all being”.
He does something similar with the expression ”body and mind”. When he describes zazen as ‘dropping off body and mind’ he’s plainly talking about this person’s body and mind— the ongoing practice of dropping off that sense of separation.
Then on other occasions, when he talks about seeing things using the whole body and mind he’s not talking about this body and mind, he’s talking about the body and mind of all being, expressed through this body and mind.
He’s able to do this because the whole of Chinese Zen rests upon the Flower Garland Sutra teachings, which is essentially that each thing in its uniqueness, in its differentiation, is all things. This person is not the same as that person, and precisely because of that, both this person and that person are all being. In this perspective, the two distinct meanings aren’t contradictory, but indicate how things really are.