Shikantaza and Jijuyu Zanmai

Shikantaza (just sitting) and Jijuyu Zanmai (self-fulfillment Samadhi)

In order to understand jijuyu zanmai, (self-receiving oneness Samadhi) one has to understand the underlying principle of shikantaza. as presented by Dogen Zenji.
Jijuyu Zanmai may be translated
ji-as self or in oneself,
ju-to receive or accept,
and Yu-to use, work or function in concentrated union. 
It implies that we receive oneness and we use it.

Samadhi has had many translations, among them concentration or single-mindedness. It is the place where there is no discrimination between you and zazen (subject and object merged).

I like Uchiyama Roshi’s translation of Samadhi as Right Acceptance. The deep acceptance of life as it is in each moment. This acceptance rests deep in our bodies. This acceptance allows us ease and the ability to patiently receive all that is happening both universal and particular. This acceptance really allows the self to settle into the self. The word settled is so evocative of the type of groundedness and stability that aligns with Samadhi.

Shikantaza also has various meanings. 
Shikan means just or only.
Ta means to hit.
Za means to sit

Literally it means to hit “sitting” exactly on the nose of the moment. The “ta” really intensifies the sitting.

Tenshin Reb Anderson spoke about this:

“If you do your part and you put” just sitting” out there, you will get a response called enlightenment. It’s already there, completely pervading you already but you just have to put a little energy forward in order to realize it. It’s not exactly a little energy or a lot of energy. But just the energy of this moment, whatever it is. That’s why you don’t need anything else but what you’ve already got.”

In sitting practice, the mind stops at the direct and immediate bodily experience. As Uchiyama roshi teaches, one can be constantly opening the hand of thought and letting our thoughts, ideas, and elaborations go. ‘Just sitting’ practice is just the mind terminating on the concept of sitting. Isn’t that a great word, “terminating”? Our minds just stay with the body, the mind and the breath, sitting.

Katagiri roshi writes, “This is zazen, without any expectation at all. It is spinning in dynamism, interconnected with the universe. In this interconnection, all sentient beings are completely absorbed into zazen itself.”

Katagiri roshi continues to say that this Zazen itself is the practice of Buddha. Zazen itself is non-doing. This zazen is the real form of the self. Zazen is a very pure sense of human activity. We stop believing concepts and have no fabrication. In doing zazen, the thoughts and fantasies arise but we return to zazen by letting them go.

This is called jijuyu Samadhi — the manifestation of simplicity.