Ecclesiastical letter
Ecclesiastical letters are publications or announcements of the organs of Roman Catholic ecclesiastical authority, e.g. the synods, but more particularly of pope and bishops, addressed to the faithful in the form of letters.
Letters of the Popes in the period of the early church
The popes began early, by virtue of the Primacy of the Roman Pontiff, to issue canon laws as well for the entire Church as for individuals, in the form of letters which popes sent either of their own will or when application was made to them by synods, bishops or individual Christians.
Apart from the Epistles of the Apostle Peter, the first example of this is the Letter of Pope Clement I (90-99?) to the Corinthians, in whose community there was grave dissension. Only a few papal letters of the first three Christian centuries have been preserved in whole or part, or are known from the works of ecclesiastical writers. Among them are Adversus Aleatores by Pope Victor I, some fragments of a letter by Pope Stephen I, three letters by Pope Cornelius, and one by Pope Dionysius. As soon as the Church was recognized by the (Roman) State and could freely spread in all directions, the papal primacy of necessity began to develop, and from this time on the number of papal letters increased.