, is a term used in Zen Buddhism to denote a high-level of certification, and literally means "the legitimate seal of clearly furnished proof." In ancient times inka usually came in the form of an actual document, but this practice is no longer commonplace. A qualified Zen master

Zen master

Zen master is an umbrella title sometimes used to refer to an individual who has been recognized by an authorized Zen lineage holder and teacher as having met his or her own teacher's standards of realization or insight. These standards vary widely in different traditions, and may vary among...

 bestows inka only upon his or her students that have demonstrated themselves as leaders and capable of teaching.

James H. Austin writes that, "The ideogram for inka has two parts: in is on one side, ka is on the other. The root meaning resides in the character for in (yin in Chinese). The right half of this in consists of an ancient character shaped like our modern P. In ancient times the character represented an actual object. It stood for the image of just the right half (P) of the emperor's official seal (IP), after the Emperor had broken in half the whole seal." The right-hand portion of the seal was given to an individual who would then work by authority of the emperor, while the emperor himself would retain the left-hand portion. In the Rinzai school

Rinzai school

The Rinzai school is , one of three sects of Zen in Japanese Buddhism.Rinzai is the Japanese line of the Chinese Linji school, which was founded during the Tang Dynasty by Linji Yixuan...

 of Zen, inka is the official indicator of mastery and indicates an individual who has successfully completed the curriculum of koan practice.

According to Peter Matthiessen

Peter Matthiessen

Peter Matthiessen is a two-time National Book Award-winning American novelist and non-fiction writer, as well as an environmental activist...

, "In the Rinzai tradition, inka is equivalent to dharma transmission

Dharma transmission

Dharma transmission refers to "the manner in which the teaching, or Dharma, is passed from a Zen master to their disciple and heir...

."

In other schools, such as the Harada-Yasutani school, inka is approval that goes beyond Dharma transmission—granted to a master who is confirmed to be, "an enlightened successor of the Buddha." In the Kwan Um School of Zen

Kwan Um School of Zen

The Kwan Um School of Zen is an international school of Zen centers and groups, founded in 1983 by Seung Sahn Soen Sa Nim. The school's international head temple is located at the Providence Zen Center in Cumberland, Rhode Island, which was founded in 1972 shortly after Seung Sahn first came to...

, inga is not associated with Dharma transmission at all. Rather, it denotes that the individual is a Ji Do Poep Sa Nim and can lead retreats and teach koan practice to others. The Japanese

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 Sōtō

Soto

Sōtō Zen , or is, with Rinzai and Ōbaku, one of the three most populous sects of Zen in Japanese Buddhism.The Sōtō sect was first established as the Caodong sect during the Tang Dynasty in China by Dongshan Liangjie in the 9th century, which Dōgen Zenji then brought to Japan in the 13th century...

 school also confers inka shōmyō (or inshō) upon students—meaning "'[granting] the seal of approval to a realization of enlightenment'"—and the student must undergo a shiho

Shiho

refers to a series of ceremonies in Sōtō Zen Buddhism wherein which a priest receives full transmission, inheriting the Dharma from his/her master and becoming empowered to transmit the precepts and lineage to others. A shiho ceremony can last anywhere from one to three weeks, with the final...

ceremony to receive Dharma transmission.