The apostles used letters to address the faithful of the various churches they had helped to establish. Most notably, St. Paul wrote a number of letters (epistles), 21 of which are included in the canon of the New Testament. Their successors, the bishops, followed this practice and would often send letters to one another and to the members of the particular churches entrusted to their pastoral care in order to ensure consistency in faith and practice, especially with regard to the celebration of the liturgy. The Bishop of Rome himself would write letters to be circulated to all the bishops. He also received letters from the bishops, which he, in turn, would circulate to other bishops.
During the Middle Ages, the practice of sending these letters fell into disuse. During this time, the popes would send letters only to individual bishops about particular matters within their dioceses. Bishops would respond in writing only to the pope.
Pope Benedict XIV (r. 1740-58), wisely employing the power of the newly invented printing press, revived the ancient practice of the pope writing letters to all the bishops of the world. It was Pope Gregory XVI who applied the term “encyclical” to these letters, from the Latin word encyclicus, or circular, because they were addressed to the entire Church. Since 1740, popes have produced nearly 300 encyclical letters, which have addressed any number of issues pertaining to the life and ministry of the Church.
