Need I mention the Buddha, who was possessed of inborn knowledge? The influence of his six years of upright sitting is noticeable still. Or Bodhidharma's transmission of the mind-seal?--the fame of his nine years of wall-sitting is celebrated to this day. Since this was the case with the saints of old, how can we today dispense with negotiation of the Way?
You should therefore cease from practice based on intellectual understanding, pursuing words and following after speech, and learn the backward step that turns your light inwardly to illuminate your self. Body and mind of themselves will drop away, and your original face will be manifest. If you want to attain suchness, you should practice suchness without delay.
What Dogen is saying here is that even Shakyamuni Buddha and Bodhidharma with their incredible talent for the dharma and attainment needed to practice intensely in sitting meditation for years. Therefore the notion that such practice is unnecessary is absurd.
Dogen was a Buddhist reformer who wanted to restore true Buddhist practice in place of what he saw as the degenerated forms of Buddhism that had become prevalent in Japan. The time Dogen was writing was a period of transition for Buddhism. The traditional schools of Tendai (Mahayana) and Shingon (Vajrayana) were becoming overshadowed by new, populist, lay-dominated sects that placed no emphasis on meditation. These sects argued (as they still do) that they were in the degenerate final age according to Buddhist mythology and that realisation through individual effort ('self-power') had become impossible - only so called 'other-power' could bring sentient beings to salvation, so they put faith in chanting the Nembutsu - the name of the Bodhisattva of compassion, Amida Buddha - NAMU AMIDA BUTSU (in Pure Land Buddhism) or a line from the Lotus Sutra, NAM-MYOHO-RENGE-KYO 'the teaching of the lotus flower of the wonderful law' (in Nichiren Buddhism). I suspect Dogen's comments were made with this in mind.
This matter is explored in more detail in the Bendowa:
Questioner: Such reasons as correct transmission by the unexcelled method of the Tathagatas and following in the footsteps of the patriarchs are beyond common sense. To ordinary people, reading the sutra and saying the Nembutsu are the natural means to enlightenment. You just sit cross-legged and do nothing. How is this a means to enlightenment?
Dogen: You look on the meditation of the Buddhas and the supreme law as just sitting and doing nothing. You disparage Mahayana Buddhism. Your delusion is deep; you are like someone in the middle of the ocean crying out for water....What good are such actions as reading the sutras and saying the Nembutsu. How futile to think that Buddhist merits accrue from merely moving the tongue and raising the voice. If you think this covers Buddhism, you are far from the truth. Your only purpose in reading the sutras should be to learn thoroughly that the Buddha taught the rules of gradual and sudden training and that by practicing his teachings you can obtain enlightenment. You should not read the sutras merely to pretend to wisdom through vain intellections. To strive for the goal of Buddhism by reading many sutras is like pointing the hill to the north and heading south. It is like putting a square peg in a round hole. While you look at words and phrases, the path of your training remains dark. This is as worthless as a doctor who forgets his prescription. Constant repetition of the Nembutsu is also worthless-like a frog in a spring field croaking night and day.
Dogen is also criticising merely intellectual understandings of Buddhism and fixation with sutras and other inherited literature. For Dogen, the true meaning of Buddhism - realisation itself - is not something that we can truly grasp with the intellectual mind but is something to be realised directly, primarily through meditation. This is what he means when he says:
learn the backward step that turns your light inwardly to illuminate your self
From this expression it is clear that for Dogen, sitting meditation (zazen) is not just a matter of sitting immobile in a particular posture with the mind doing as it will as some have claimed. Zazen - even when called 'just sitting' - is not some kind of purely physical practice or stationary yoga. It is not as Dogen says "just sitting and doing nothing". It is learning the backward step and turning the mind inwardly. The backward step is an interesting expression which suggests to me the abandonment of the mind of 'doing' or 'achievement' or 'changing the ways things are', and being concerned rather with reality, just as it is. Turning your light inwardly in an expression that may derive from a teaching that Shakyamuni Buddha gave on his deathbed. In the Zen tradition this teaching is passed down in the Pali language in the form of the Atta Dipa:
You are the light itself
Rely on yourself
Do not rely on others
The Dharma is the light
Rely on the Dharma
Do not rely on anything
Other than the Dharma
I suspect that Dogen did not have direct access to the Nikayas of the Pali Canon (which are likely to be the most accurate renderings of the teachings of Shakyamuni Buddha). He probably relied on paraphrased versions which were passed on orally, in Mahayana Sutras or in gathas such as the Atta Dipa. A more full and accurate version of these words are found in the Maha-Parinibbana Sutra - they are a response to Ananda, his most senior disciple, who asks him how they should continue their practice after the Buddha's death.
"Now I am frail, Ananda, old, aged, far gone in years. This is my eightieth year, and my life is spent. Even as an old cart, Ananda, is held together with much difficulty, so the body of the Tathagata is kept going only with supports. It is, Ananda, only when the Tathagata, disregarding external objects, with the cessation of certain feelings, attains to and abides in the signless concentration of mind, that his body is more comfortable.
"Therefore, Ananda, be islands unto yourselves, refuges unto yourselves, seeking no external refuge; with the Dhamma as your island, the Dhamma as your refuge, seeking no other refuge.
"And how, Ananda, is a bhikkhu an island unto himself, a refuge unto himself, seeking no external refuge; with the Dhamma as his island, the Dhamma as his refuge, seeking no other refuge?
"When he dwells contemplating the body in the body, earnestly, clearly comprehending, and mindfully, after having overcome desire and sorrow in regard to the world; when he dwells contemplating feelings in feelings, the mind in the mind, and mental objects in mental objects, earnestly, clearly comprehending, and mindfully, after having overcome desire and sorrow in regard to the world, then, truly, he is an island unto himself, a refuge unto himself, seeking no external refuge; having the Dhamma as his island, the Dhamma as his refuge, seeking no other refuge.
"Those bhikkhus of mine, Ananda, who now or after I am gone, abide as an island unto themselves, as a refuge unto themselves, seeking no other refuge; having the Dhamma as their island and refuge, seeking no other refuge: it is they who will become the highest, if they have the desire to learn."
The essential meaning is the same, although the absence of any reference to 'light' in the earlier Sutta implies that we shouldn't look too hard for any special significance of it in the Atta Dipa.
What does Dogen mean by turning your light inwardly and illuminate your self? It means to be aware and present in the here and now, recognising that the mental phenomena of one's own personal mind are empty, impermanent, and not-self. Only in the clarity of non-grasping awareness can we see what we are not and thus gain insight into true nature. In other words, he is describing a kind of meditation that is called vipassana or mindfulness in other traditions, perhaps more accurately 'objectless awareness' or 'themeless meditation', which in Soto Zen is called 'silent illumination' or 'just sitting'.
As in most schools of Buddhism, some, 'Zennists' like to set their practice apart from (and above) other schools, however understood correctly, all authentic schools of Zen are a transmission of a core of understanding and meditation practices from Shakyamuni Buddha through the Zen Patriarchs to today (although there have been some simplifications and some developments too). Shakyamuni Buddha practiced Vipassana or Mindfulness meditation as described in detail in the Pali Canon. Just before his enlightenment he was practicing the most advanced of these practices, referred to as 'themeless meditation'. I believe that this corresponds to Shikantaza and like all mindfulness meditation involves maintaining awareness of the present moment when it gets involved in thinking and dreaming. It does not allow the mind to do what it will without discipline.
The Fukanzazengi continues:
Body and mind of themselves will drop away, and your original face will be manifest.
This is a phrase that comes up again and again in Dogen and refers to his own awakening experience under the instruction of Master Nyōjo. For example, it is found in this famous passage from the Genjokoan:
To study the buddha way is to study the self. To study the self is to forget the self. To forget the self is to be actualized by myriad things. When actualized by myriad things, your body and mind as well as the bodies and minds of others drop away. No trace of realization remains, and this no-trace continues endlessly.
I think that body and mind dropping away refers to the total disappearance of the sense of oneself as a discrete being at both a physical and psychic level or the collapse of subject-object duality. In other words, it is deep Zen samadhi. This is seeing directly with one's own eyes the false nature of the constructed sense of self and that one's true identity is reality itself, this moment itself, the universe itself or expressed in another way, no identity. This is one's original face becoming manifest. Original face becoming manifest is a common expression for realisation, or seeing one's true nature in the Zen tradition, which has it's roots in the following koan:
Huìnéng asked Hui Ming, "Without thinking of good or evil, show me your original face before your mother and father were born."
The text continues:
If you want to attain suchness, you should practice suchness without delay.
Dogen is saying that if you wish to attain freedom from delusion, aversion and craving, rather than relying on intellectual knowledge or faith in the power of chanted phrases, we must practice the activity of being free from delusion, aversion and craving. The direct identification between the 'suchness' that is attained and the 'suchness' that is practiced can be seen as a reference to Dogen's doctrine of practice-enlightenment - that is, the non-separation of practice and attainment.