The common medieval image was that of three orders. Yet each component was described as an ordo. My point here is not to argue for the retention of a title, especially a title that takes so many pages of explanation. That division is, as Father Congar points out, the basis for the canonical distinction between clergy and laity, those who hold office in the church and those who do not. There is unity but there is also diversity.
Ternary views are the despair of a theocratic clergy or a caesaropapist government.
Authority, even if acknowledged to be of God, must be seen as deriving in various ways and refracted in different modes, and set forth in different groups. The very common division of the three orders into those who fought, those who prayed, and those who worked, testifies to the complexity. It was obvious to medieval folk that there were connections between all things. Thus, after 1100, when Western Europe entered a period of economic, social, political, and cultural change it was obvi ous that there was bound also to be religious change. Inevitably they impinged upon the idea of orders.