A conventional term for certain ceremonies in use from time immemorial among the Chinese, which the Jesuit missionaries allowed their neophytes to retain after conversion, but which were afterward prohibited by the Holy See.
These rites had to do with honoring ancestors or deceased relatives and paying particular tokens of respect to the great Chinese master, Confucius.
Father Matteo Ricci, SJ, founder of the Catholic missions of China, in his endeavor to be as tolerant as possible of Chinese customs which did not manifestly interfere with the purity of the Christian religion, considered that these rites might be continued on the ground that they were not religious ceremonies.
After 1630 other religious orders established missions in China, and much controversy sprang up with regard to the rites.
The methods of the Jesuits were bitterly, sometimes unjustly, attacked.
After a long period of misunderstanding the Holy See forbade the rites to the Chinese converts, declaring that the ceremonies in honor of Confucius or ancestors and deceased relatives are tainted with superstition to such a degree that they cannot be purified.
This decision is contained in the Apostolic Constitution "Ex ilIa die" issued by Clement XI, 19 March 1715, and in the Bull "Ex quo singulari" issued by Benedict XIV, 11 July 1742.
Ricci's error was one of judgment and not of faith or morals.
To safeguard the reputation of the holy missionary the Holy See forbade it to be said that Father Ricci approved idolatry.
New Catholic Dictionary