Dogen's Zen

Here's my fairly simple and straightforward take on Dogen's Zen. Shikantaza has two elements: body posture (taza) and mental posture (shika). The physical posture requires little elaboration (kek/hankafuza). The mental part is hishiryo, what I like to put as "neither-thinking", although the usual wording is "non-thinking", but the meaning of it is not different from what Changlu Zongze (in Zuochan Yi, the source of Dogen's Zazengi), Guifeng Zongmi (in Chan Letter (see: Zongmi on Chan, p 88)), and Dajian Huineng (or rather Heze Shenhui) identified as the very essence of Zen: no-thought (wunian/munen). Now the definition of hishiryo/munen, as provided in the Sotoshu's website (How to do Zazen): "When various thoughts arise in your mind, do not become caught up by them or struggle with them; neither pursue nor try to escape from them. Just leave thoughts alone, allowing them to come up and go away freely." And Okumura (Zazen Instruction): "That means you let go of whatever thoughts come up, and you also don’t sleep. This is the point in our sitting practice." How does that equal enlightenment (or rather confirmation-realisation)? Because it directly perceives that appearances are unobtainable (anupalabdha / fukatoku), i.e. empty.
The idea of practice-enlightenment is another instance/version of direct/sudden enlightenment, and Dogen's twist on the matter, as I see it, is rather a reaction to correct the possible mistakes of Kanna Zen and other misinterpretations that can be associated with it, hence his rejection of kensho as well.
So, is Shikantaza a shamatha practice, a vipashyana practice, both, neither? Partly, that is irrelevant, because those terms need further clarification, and then one just ends up comparing one interpretation of them with Zen. If one wants the general Zen answer, then check out the Platform Sutra on samadhi and prajna in chapter 4 (BDK ed, p 42): "It is like the light of a lamp. When the lamp exists, there is light; when there is no lamp, there is darkness. The lamp is the essence of the light, and the light is the function of the lamp. Although the names are different, in essence they are fundamentally identical. The Dharma of meditation and wisdom is just like this."
Why are there no thousands of buddhas already if merely sitting in zazen is enlightenment? The question is quite like the legendary story about Dogen's reason for travelling to China (i.e. Why practise if we're already buddhas?). And the answer is not that enlightenment needs to be enacted (at least according to me, contradicting the popular Soto idea of the matter), but because of what Zongmi and others talked of regarding "sudden enlightenment, gradual practice", that one needs to work on one's habitual proclivities and attachments. This is rather standard Buddhism, where a stream-enterer (or 1st bhumi arya-bodhisattva) has the certainty about the path and the goal, but still has to walk that path with the correct view already established.

Excerpts from the Mahayanasutralamkara

THE STAGES BY WHICH THE ULTIMATE, THATNESS, IS REALIZED
(7.6-9)

Bodhisattvas, going beyond infinite merit and wisdom,
Perfectly gather the accumulations, and then
Reflect and gain perfect certainty with regard to the Dharma.
As a result, they realize objects to be the products of expression.
Once they see that things are merely expressions,
They dwell in the truth that it is mind alone that appears as those things.
After that they gain direct realization
Of the expanse of reality, free of the characteristics of duality.
From intellectual understanding that there is nothing other than the mind,
They then realize that neither does the mind exist.
Once the wise have seen that both do not exist,
They abide in the expanse of reality devoid of those.
The power of nonconceptual gnosis in the wise
Constantly extends to everything in equal measure,
And clears away the dense jungle of the faults they bear
Like a universal antidote removing poison.

THE CAUSE FOR ATTAINING COMPLETE PURITY
(10.78-79)

That which does not exist
Is held to be the sublime existence.
Not conceptualizing in any way
Is held to be the sublime conceptualization.
Meditation that does not look at aspects
Is held to be the sublime meditation.
The attainment of those who do not look
To attain anything is also held to be sublime.

FOLLOWING THE GREAT VEHICLE WITHOUT GETTING DISCOURAGED
(11.12)

Sentient beings born as humans,
In infinite numbers, in every instant,
Attain perfect enlightenment,
So do not give in to losing heart.

INVESTIGATING THE ILLUSION-LIKE NATURE OF PHENOMENA
(12.15-22)

Of false imagination,
We say it is like a magical illusion;
And of dualistic delusion,
We say it is like the forms in a magical illusion.
In the same way that there is nothing in an illusion,
We accept the ultimate truth.
And in the same way that it is perceived,
We accept the relative truth.
Just as when the illusions are not there
And their causes are clearly seen,
When transformation takes place,
One perceives the false imagination.
Undeceived people
Use the illusion’s causes as they wish.
So too, those who are diligent in the precepts, undeluded,
Experience the transformed state as they please.
Though they are there in appearance,
It is not that they really exist.
Thus we say that in magical illusions and the like
Things exist and do not exist.
It is not that what is there does not exist,
Nor that what is not there exists.
In magical illusions and the like
We do not distinguish between their existence and nonexistence.

THE REASON FOR TEACHING THE DHARMA
(13.2-3)

Because it is to be known by oneself, Lord Buddha did not teach the Dharma;
Yet with the breath of his teachings, rationally explained, the embodiment of compassion, like a python,
Draws beings onto the path, setting them perfectly in the mouth of total peace,
Utterly pure, vast, common, and inexhaustible.
Consequently, no practitioner’s meditation is pointless,
And thus neither are the teachings of the sugatas pointless.
If one could see the meaning simply by listening, there would be no point in meditating,
And if one could practice meditation without having listened, there would be no point in teaching.

NONCONCEPTUAL WISDOM
(14.16-19)

Phenomena do not exist yet are perceived;
Defilement does not exist and yet is purified;
Know that they are like magical illusions and so forth,
And likewise that they are like space.
Just as on a well-drawn picture
There are no different planes, yet there seem to be,
To the false imagination, duality,
Though never there, appears in different ways.
When muddy water becomes clear,
Its clarity is not something produced from the muddy state,
But rather the removal of the dirt contaminating it.
So it is with the purity of one’s own mind.
The mind is held to be eternally natural clear light;
It is coarsened by adventitious faults.
The mind is ultimate reality, and there is no other mind but clear
light.
We speak of this as the nature of mind.

THE LOVE AND COMPASSION THAT NEVER FORSAKES SENTIENT BEINGS
(14.20-23)

Bodhisattvas feel for sentient beings
A heartfelt love as great as that
Felt for an only child—
Their constant wish is to bring them help.
Because it brings benefit to sentient beings,
The fondness bodhisattvas feel does not become a downfall.
But hatred in them will always violate
And act against all beings.
Like doves who love their young the most,
Staying with them and holding them close,
With not the slightest place for anger,
Are those whose hearts are full of love for beings, their children.
Because they love, there’s never room for rage.
Because they pacify, malice is out of place.
Because they benefit, they never think deceitfully.
Because they comfort, they’ll never terrify.

KEEPING THE INSTRUCTIONS IN MIND BY REFLECTING
(15.8)

The summarization of the scriptures in their titles
Should be understood as being the path of sustained calm.
The path of profound insight
Should be understood as the analysis of their meaning.

KEEPING THE INSTRUCTIONS IN MIND BY MEDITATING
(15.16-18)

From striving for preternatural knowledge,
They are purified and become supremely fit.
By using the preternatural powers
Gained through concentration,
In order to venerate and listen to
Countless buddhas
They travel to different worlds.
Thus they venerate infinite buddhas
For infinite kalpas.
And because they have venerated them,
Their minds become supremely fit.

HOW BODHISATTVAS PROGRESS FURTHER ALONG THE PATH
(15.23)

Next, bodhisattvas like these
Remain in evenness, and by doing so,
No longer see any objects
As anything other than mental expressions.

ESTABLISHING THE INDIVIDUAL NO-SELF
(19.93-95)

An individual is to be expressed
As existing as a designation; it is not substantial.
It cannot be perceived, is a mistaken notion,
And is the cause of the defilement process and the defilements.
On account of two faults, it cannot be described
As identical to or different from the aggregates,
For they would then be the self
Or it would be a substantial thing.
If it exists substantially, it is necessary to provide
The reason why it cannot be described.
To say that it cannot be described as being the same or different
Without giving a reason is inadmissible.

(All quotes are from the Ornament of the Mahayana Sutras, published in A Feast of the Nextar of the Supreme Vehicle, translated by the Padmakara Translation Group)

Essence and Function of the Zen Mind

Zen deals with the mind, and the mind is often described with two concepts: essence and function. In essence the mind is empty and pure. In function it is whatever occurs, all phenomena. Essence and function are not two different things, not two separate minds, but simply one common way to describe the mind. There is no essence without function, and there is no function without essence. But one can make the mistake of grasping only one of them, or dividing them.

Delusion is being fooled by function, where one is attached to one's thoughts, feelings, and sensory impressions.
Beginning practitioners are often fooled by essence, where they want only peace, motionlessness, transcendence, the absolute.
After some experience one recognises that dealing with function is inevitable, so there is a process of harmonisation, of balancing, of integration of the two sides.
Further on one can arrive at the point where essence and function are inseparable, where non-thought is in the midst of thought, and it becomes possible to cultivate genuine Zen.
The final stage is simply that there is no more cultivation done, no more effort needed, as essence has never been apart from function, nor function from the essence.