If a person cannot foresee the consequences of his act, and is not capable of understanding what he is told about its outcome by those with more experience, it is impossible for him to guide his act intelligently. In such a state, every act is alike to him.
Understanding one another means that objects, including sounds, have the same value for both with respect to carrying on a common pursuit.
There is no common understanding, and no community life. But in a shared activity, each person refers what he is doing to what the other is doing and vice-versa.