When I initially undertook this project, I forgot how heavily loaded the first few fascicles are in the Shobogenzo. This chapter by Dogen is actually recited during particular ceremonies in most zendos. It is probably the most often quoted work in the Shobogenzo.
A koan is a word puzzle used by Zen students to attain realization. Their main utility is to exhaust the rational mind and allow students to get in touch with their intuitive mind. Each koan tells a story that was posted on a bulletin board in monasteries. In fact, the word koan litereally translates to something like "notice board/public record."
The word genjo (げんじょ) means "realized," so genjo-koan means something like "realized universe." Taken together, the title of this chapter indicates that Dogen is descibing to us the Universe itself.
Dogen begins by describing how all phenomena (dharmas) can be viewed in different ways. We can look at themfrom the relative world, where there is practice and realization, life and death, etc.; and we can look at them in the realm of the absolute where there is no practice nor realization, no life nor death, etc. One line that is particularly memorable to me is - "and though it is like this, it is only that flowers, while loved, fall; and weeds while hated, flourish."
When we try to force balance into our lives, the ego is reinforced as we think we can change our external circumstances. It is only when we let go that we can achieve that balance. Thinking that we can achieve some state where we will never have to overcome hardships is a delusion. Realizing that conditioned existence is suffering, temporary, and not-self is achieving that state of balance. Even when you have achieved this inner peace, you may not necessarily know it.
Another notable quote from the Genjo-Koan was printed on the front of the welcome pamphlet at the Atlanta Soto Zen Center - "To learn the Buddha's truths is to learn ourselves. To learn ourselves is to forget ourselves. To forget ourselves is to be experienced by the myriad dharmas. To be experienced by the myriad dharmas is to let our own body-and-mind, and the body-and-mind of the external world, fade away." This was appropriately used as the first words a Zen student should read, because it emphasizes the importance of the Buddhist teaching, anatta (not-self).
Dogen points out that just as things in the physical world can be viewed from several perspectives, our understanding about metaphysical concepts can also be viewed from many perspectives, some of which are incorrect. The most common and pernicious of these misconceptions is that our ego-identity is either permanent, or defines some ineffible self. He makes an analogy to firewood and ash. When a fire burns out, you can't say where the fire has gone or turn the ash back into wood. We can't ever say that one thing has transitioned into another, like a person who transmigrates between human shells in a series of lives.
We can only say that things exist at one moment in a particular arrangement. However, everything disappears and reappears at a very fast rate, each stage providing a whole new universe. In this way, we cannot say that anything has a permanent self. The universe is perceived by sentient existence as being continuous despite this frequent disappearance and appearance of phenomena, just as a film consists of individual frames on a reel but appears to be a continuous video.
"A person getting realization is like the moon being reflected in water, the moon does not get wet, and the water is not broken." Even though the moon is immense, it can be entirely and perfectly reflected by miniscule drops of water. This description is used as an analogy to describe the experience of realization, which is not present if a person re-inforces their ego-identity. It is very easy to unintentionally re-inforce the ego-identity by imagining that we have perfect understanding. We might take some view as being the truth, and later discover that we hadn't yet achieved clear vision.
When we view things without making the distinction between subject and object, we attain balance. If you don't create the ego, it will not appear. If you use the ego to reduce suffering in the universe, you don't lose that balance even if you think you have. In fact, this state of balance is the universe itself, as it could be no other way. Because of this, Dogen claims that you will not necessarily realize when you attain realization, even though it happens at once, all in an instant. He expands on this by saying that the state of not achieving is the experience of realization.
The chapter concludes with the recitation of an old text which describes a student, and master, and his fan. The student questions the master, along the lines of "since the air is the way it is, why do you re-inforce you ego by using the fan [manipulating it]?" The master responds saying that the student intellectually understands that air can only be the way it is, but he does not yet know the truth of how that is so. The student asks what it means to know the truth. The master just continues fanning himself, indicating that even though there is no self, we can still observe that there is from a relative perspective and control our actions.
Some people say that one no longer has to practice zazen after their enlightenment, because things are the way they are and the realized person sees balance in everything. However, it is the act of practicing zazen that lets us experience the universe as it is. Because of these truths, there are many great sanghas all throughout the world where men and women practice zazen earnestly, and with great vigor.