The bone rank system was the system of aristocratic rank used in the ancient Korean kingdom of Silla. It was used to segregate society, and particularly the layers of the aristocracy, on the basis of their closeness to the throne and the level of authority they were permitted to wield. Bone rank was strictly hereditary, and thus acted as a caste system. Lee (1984, p. 43) considers it to have probably been adopted as part of the administrative law promulgated by King Beopheung in 520. Although only two of the five known ranks were referred to as "bone" (골, 骨), the term "bone rank" has become widely used to describe the whole system.

A person's bone-rank status governed not only official status and marriage rights, but also the permitted color of clothing and the maximum size of a person's house. These criteria are described in detail in the Korean chronicle Samguk Sagi, Ji 2. The Samguk Sagi's depiction of Silla life, however, has often been criticized for being excessively static. Unfortunately, since other sources are scarce, it is difficult to judge what sort of changes may have taken place in the bone rank system over the centuries.

The highest level of the bone-rank was the "hallowed bone" (성골,聖骨), which consisted only of a portion of the royal Kim family, possibly those considered to have royal blood on both sides. Until this rank was abolished the reign of King Muyeol in the 650s, only those holding hallowed-bone rank were permitted to be king. This led to the crowning of Queen Seondeok in 632 and Queen Jindeok in 647, because no males of the hallowed bone rank were available. That situation may have led to its subsequent abolition.

Below that came the "true bone" (진골, 眞骨), which included the rest of the royal family, as well as the Bak and Seok families of Gyeongju which had held the throne in very early times and were involved in most royal marriages, as well as another Kim lineage descended from the royal house of Geumgwan Gaya. Members of the true bone could hold any official position, up to the level of full minister. They could gain any also gain office rank up to the highest, ibeolchan (이벌찬). After the hallowed-bone rank was abolished under King Munyeol, only those holding the true bone rank could become king.

Below the "true bone" came the head ranks (두품, 頭品), of which only the 6th, 5th and 4th are attested, 6th being the highest. Members of the 6th head rank could rise to the position of vice-minister (gyeong, 경) and as high as the 6th level of office rank, achan (아찬). Members of the 5th and 4th ranks could rise only to minor posts. Members of the fifth head rank could reach the 10th level of office rank, daenaema (대내마, 大奈麻). Members of the fourth could attain only the 12th level of office rank, daesa (대사, 大舍). There were 17 levels of office rank altogether. Lee (1984, p. 50) proposes: "head-ranks three, two, and one, if they ever formally existed, must have designated the ... non-privileged general populace."

The bone-rank system's extreme rigidity may have helped to weaken Silla toward the end of the Unified Silla period, although numerous other factors were at play. After the fall of Silla, the bone-rank system was abolished, although different and somewhat more flexible caste systems persisted until near the end of the Joseon Dynasty in the late 19th century.

See also

• History of Korea
• List of Korea-related topics
• Three Kingdoms of Korea

References

Lee, K.-b. (1984). A new history of Korea. Tr. by E.W. Wagner & E.J. Schulz, based on the Korean rev. ed. of 1979. Seoul: Ilchogak. ISBN 89-337-0204-0