Soto Zen is situated within the Buddhist tradition, which began twenty five centuries ago in India and traveled along the Silk Road to China and Japan before coming to the West. Yet Dogen Zenji's shikantaza (just sitting) itself is a transparent practice that does not require a Buddhist container; thus it can be colored by any number of influences and contexts, Buddhist and not. We do only four things in shikantaza: take the posture, keep our eyes open, breathe deeply and let go of thought. Anyone from any faith tradition or none can do this and is welcome to join us in our zazen practice, so it's helpful for us to understand the basis of this transparent practice within the Sanshin style and spirit.
The first element of Sanshin's mission is to enable shikantaza in the style of Uchiyama Roshi. There are three parts to this, of which the first is the study of the meaning of zazen in the context of Buddha’s teachings, understanding the common thread that runs from the teachings of Shakyamuni through the Mahayana tradition, the teachings of Dogen Zenji, Sawaki and Uchiyama Roshis, down to Okumura Roshi and the practice of shikantaza at Sanshin today.
Okumura Roshi goes on to write: "Our zazen is based on the essential philosophy of Mahayana Buddhism -- that is, emptiness. Emptiness means no self and no other. Everything is connected as one thing. All beings are connected to each other. All beings interpenetrate each other. There’s no separation between subject and object, particularly in our zazen. The subject is this person, and the object is also this person."
When Shakyamuni realized awakening under the bodhi tree, he knew directly that clinging is the cause of suffering. He saw that we try to gratify sense desires by grasping at things we deem desirable, and that danger lies in that clinging because the loss of that desirable object is inevitable. The escape from this cycle of greed and fear is in taking up the Eightfold Path.
One of the things to which we cling most readily is the five skandhas or aggregates that make up the concept we call "me." Somehow we need to understand how five skandhas can be released from clinging to five skandhas. The Buddha taught that all conditioned things are empty of a fixed and permanent self nature because of both interdependence and impermanence. Everything arises because of causes and conditions; nothing comes into being by itself, so nothing can be separate from everything else around it (interdependence). Because these causes and conditions are changing all the time, the things that arise from them must also be changing (impermanence). If everything is connected to everything else and changing all the time, there's nothing we can identify as a permanent self-nature or essence -- and Buddha's teaching about emptiness must include this group of five skandhas called "me." This is also the teaching of the Prajna Paramita literature in the Mahayana tradition. The Heart Sutra says, "Avalokitesvara Bodhisattva, when deeply practicing prajna paramita, clearly saw that all five aggregates are empty and thus relieved all suffering."
The five skandhas being free from clinging to five skandhas on the basis of emptiness is the equivalent of Dogen Zenji’s shinjin datsuraku (dropping off body and mind), Sawaki Roshi’s “zazen is good for nothing,” Uchiyama Roshi’s “opening the hand of thought” and Okumura Roshi’s “1=0=∞ (infinity).“ This is what we actualize in shikantaza, which has been handed down to us directly from generation to generation.