Osho,
Dogen continues:
When we look around our boat on the mountainless ocean, we see nothing but the circular shape of the ocean. But this large ocean is not circular or square; its other shapes and movements are innumerable. To fish it is like a palace. To celestial beings it is like a necklace. Only as far as the eye can reach, does it temporarily appear circular.
This is also the case with all things. All things worldly and unworldly have various aspects, but we can see and realize them only through practical understanding….
However far fish sail in the water, there is no end to the water. However far birds fly in the sky, there is no end to the sky. But neither of them has ever left the water or the sky.
When their need is great, there is great activity; when their need is small, there is little activity. Thus they never fail to express their full ability in each thing, and exert their free activity in each place.
But as soon as a bird leaves the sky, it dies. This is also the case when a fish leaves the water. We can realize that the water is life to the fish; that the sky is life to the bird; that the bird is life to the sky; the fish is life to the water; that life is a bird, or that life is the fish. About this there may be many other expressions.
In the human world there are practice and enlightenment, or long life and short life. This is also the real state of things. Nevertheless, if a bird or fish tries to go through the sky or the water after knowing it completely, it will find no way to go along or no place to attain.

Maneesha, Eastern mysticism has accepted layers of reality. Western science knows only one reality – that of matter. It is poor, it lacks variety. The Eastern mysticism, of which Zen is just the ultimate peak, accepts the reality of your inner self which you cannot see, cannot understand, but which you are. You can be awakened to it or you can remain asleep, it makes no difference to the inner quality of your being. That is your ultimate reality.

Then there is the body, which is only an appearance – an appearance in the sense that it is changing constantly. You see a beautiful woman or a beautiful man and they are already becoming old. The moment you rejoice in the beauty of a rose, the time for it to disappear back into the earth is not far away. This kind of reality has also its place in the Eastern vision. They call it appearance, moment to moment changing. There is a time to be born and there is a time to die. The seasons will come again, and the flowers will blossom again. It is the round trip of existence in which – except your being, your center – everything goes on changing. This changing world is a relative reality.

And then there are other realities – like dreams. You know they are not, but still you see them. Not only do you see them, they affect you. If you have a nightmare and you wake up, you will see your heart is beating harder, your breath is changed by the nightmare. You may be even perspiring out of fear. You cannot say that the nightmare is not there; otherwise from where has this perspiration come, and this changed heartbeat and breathing?

Eastern mysticism accepts this third layer of reality: the dream, the horizon that you see all around, which exists nowhere…but you can see it from anywhere.

Before I explain Dogen to you, let this be the introduction, because this is what he is trying to say: that everything passes and yet there is something that never passes; that everything is born and dies and yet there is something that is never born and never dies. And unless you get centered into that eternal source you will not find peace, you will not find serenity, you will not find blissfulness, you will not find contentment. You will not feel at home, at ease in the universe. You will remain just an accident, you will never become essential.

And the whole effort of Zen, or any meditative method, is to bring you closer to that which never changes, that which is always. It knows no time…. If there is no change, how can there be past, future, present? The world that knows past, future and present can only be relatively real – today it is there, tomorrow it is gone. The body you had believed in so much one day dies. The mind you had believed in so much does not follow you, it dies with the body. It has been a part of the body mechanism.