A line in Shobogenzo, Genjokoan, says:
And though it is like this, it is plainly that flowers, while loved, fall and weeds while hated, flourish.
This line may be the most direct expression in the whole Shobogenzo. It may also be the most widely misunderstood. It is often interpreted as an analogy, which completely misses, and even subverts the point Dogen was making. In fact, Dogen points out that the previous three lines are analogical with the words, “it is like this.” In this line, he points out that reality is not like anything: it is simply reality; that is, “flowers fall…weeds flourish.”
This corresponds with the meaning of the often-quoted Zen dictum “a separate transmission outside the scriptures, not dependent on words and letters.” This does not mean that Zen disregards scriptures and texts, but that the reality the scriptures indicate is separate from the scriptures themselves, and not dependent on the words and letters that are used to indicate it.
Zen teachings require us to see into the words, while avoiding becoming attached to the words. We cannot “learn” Zen through reading and study, but we cannot disregard reading and study either. To use an analogy: reading a recipe for chocolate cake will not result in producing a chocolate cake—you must possess the ingredients and follow the instructions. At the same time, simply possessing the ingredients without the knowledge provided by the recipe will not do either.
In the first three statements of Genjokoan, Dogen illustrates what reality is like; in this line, he presents it more directly, “and though it is like this, it is only that flowers, while loved, fall; and weeds while hated, flourish.” This kind of expression, common in Zen literature, is meant to convey the truth that reality, or enlightenment is not produced by words, knowledge, or even spiritual practice; reality is reality, as it is here and now.
After laying the foundation in the first four lines of Genjokoan, Dogen methodically builds the structural framework upon which he spent the rest of his life fleshing out; the function and essence of “The rightly-transmitted Buddha-Dharma.”