3. Without prejudice to the power which each Bishop enjoys by divine institution in his own particular Church, the consciousness of being part of an undivided body has caused Bishops throughout the Church's history to employ, in the fulfilment of their mission, means, structures and ways of communicating which express their communion and solicitude for all the Churches, and prolong the very life of the College of the Apostles: pastoral cooperation, consultation, mutual assistance, etc.

From the first centuries on, the reality of this communion has found an outstanding and typical expression in the holding of Councils. Worthy of mention among these are, together with the Ecumenical Councils which began with the Council of Nicaea in 325, the Particular Councils, both plenary and provincial, which were frequently held throughout the Church from the second century on.(²⁴)

The practice of holding Particular Councils continued throughout the Middle Ages. Following the Council of Trent (1545-1563), however, they became less frequent. Nevertheless, the 1917 Code of Canon Law, seeking to revitalize so venerable an institution, included provisions for the celebration of Particular Councils. Canon 281 of that Code spoke of the plenary Council and laid down that it could be held with the authorization of the Supreme Pontiff, who would designate a delegate to convene the Council and preside over it. The same Code called for provincial Councils to be held at least every twenty years (²⁵) and conferences or assemblies of the Bishops in each province to be held at least every five years, in order to deal with the problems of the Dioceses and prepare for the provincial Council.(²⁶) The new Code of Canon Law of 1983 retains a considerable body of laws governing Particular Councils, both plenary and provincial.(²⁷)