According to the medieval bishop, what he meant by the statement in the question is that: the three groups of people are united as one to form a society.
He believed that society is divided into three, even though we see it as one.
However, despite the division, each group cannot work separately unless they function together as one.
According to the Bishop, each of the groups works in tandem on the needs of other groups, and that is what makes the society work.
The statement was made by Bishop Adalbero of Laon, France, in 1020.
Hence, in this case, it is concluded that the medievalBishop is trying to explain the nature of the society categorized into three groups.
