Buddhism started off in India about 2,500 years ago. It was begun by a man named Gautama who was the son of the king of a small kingdom. Gautama had a very comfortable life as the son of the king. But he eventually began to wonder about “the meaning of life” and whether there was any kind of real truth. When he was 29 he decided to leave his family and his home to try to find some kind of truth. Gautama visited different teachers and tried different methods that they told him would help him. But after about seven years he reached a point where he'd became very thin and frail, and he began to wonder if there might not be a better way to find some kind of truth.
He left the small group of ascetics he was practicing with and started to eat and drink properly again. He also began to consider about what might be a better way to find the truth. At that time, he recalled an experience he had sitting under a tree as a teenager. He remembered the good feeling he had when he was just sitting under the tree. So he decided to try that kind of sitting again. He found a nice tree near a river bank, and began to sit under the tree in the cross-legged posture. This time, though, he just sat there without any particular aim. He wasn’t thinking about mantras or enlightenment or things like that. He just sat there in the cross-legged posture.
The story goes that one morning while he was sitting under the tree, Gautama saw a star in the morning sky and was awakened. After that he devoted his life to teaching other people what he had discovered. The basis for what Gautama Buddha taught people was the simple sitting that he had done under the tree. Gradually more people joined him and Buddhism slowly spread.
One of the places that Buddhism spread to was China. In those days, the main link between India and China was the Silk Road, which was a series of routes connecting East and West Asia. The early Buddhist monks made there way along the Silk Road and eventually reached China. It’s impossible to know exactly when Buddhism arrived in China, but it seems to have arrived there by around the second century AD. Some Chinese people who heard about Buddhism went to India to learn more. These people then translated some of the sutras they came across in India into Chinese.
So some Chinese people were already familiar with Buddhist ideas by the time the legendary Indian monk Bodhidharma is said to have arrived there around the fifth or sixth century. Bodhidharma is traditionally considered to be the transmitter of “Zen” Buddhism to China. He emphasized the importance of the simple sitting practice that Gautama Buddha used to do. There are a lot of legends surrounding Bodhidharma, although it’s impossible to know how accurate they are. One legend is that Bodhidharma spent nine years doing zazen at a cave in Northern China. This made the early Chinese Buddhists more aware of the importance of zazen. Up to the time of Bodhidharma’s arrival, the people teaching Buddhism in China had focused on Buddhist sutras and ideas, and not placed a great emphasis on the sitting practice. So when the Chinese saw the monk Bodhidharma doing this sitting practice so often, they thought it must be some kind of special Buddhist sect. So they gave it the name “Chan” (or “Zen”) Buddhism. “Chan” is a Chinese word that means “meditation”. But for Bodhidharma it was just Buddhism.
People were still doing that simple sitting practice 700 years later when a Japanese monk named Dogen arrived in China looking for a teacher. Dogen had studied Buddhism in Japan with the Tendai Sect and the Rinzai Sect prior to going to China. But he wasn’t satisfied with the Buddhism that he was learning in Japan. He felt that he needed to meet a true teacher to find out what Buddhism was really about. So Dogen decided to travel to China to search for a teacher.
But when Dogen got to China he was a little disappointed. Most of the temples he visited belonged to masters in the Rinzai sect. So Dogen ended up encountering the same kind of Buddhist teachers that he’d met in Japan. He travelled around China for two years but still couldn’t meet a teacher who could help him. He was just about to give up his search, when he met an old monk who told him to visit a temple called Keitoku-ji. A new abbot, Master Tendo Nyojo, had just been installed at Keitoku-ji, and the old monk told Dogen that Master Tendo Nyojo might be the teacher he was looking for.
Dogen had already been to Keitoku-ji temple once. But at that time there was a different abbot there. So Dogen went to Keitoku-ji temple and met Master Tendo Nyojo. When Dogen met Tendo Nyojo he was sure that he'd found the teacher he’d been searching for. Dogen stayed in China for two more years to study with Tendo Nyojo, and then returned to Japan.
The main thing Dogen learned from Master Tendo Nyojo was that just sitting in zazen is Buddhism itself. Master Tendo Nyojo used the phrase shikantaza to explain this to Master Dogen.
Nowadays, shikantaza is a well-known phrase in Zen Buddhism. It's made up of four Chinese characters 只管打坐. These characters are usually translated by dividing them into pairs.
The first pair is 只管 (shi-kan).
This means: nothing but / earnestly / entirely / single-mindedly.
The second pair is 打坐 (ta-za).
This means: to do sitting.
So the four characters in shi-kan-ta-za together mean:
nothing but to do sitting,
earnestly to do sitting,
entirely to do sitting,
single-mindedly to do sitting.
Take your pick.