Friends need not agree in everything or go always together, or have no comparable other friendships of the same intimacy. On the contrary, in friendship union is more about ideal things: and in that sense it is more ideal and less subject to trouble than marriage is.
One may discover a new side to his most intimate friend when for the first time he hears him speak in public. He will be stranger to him as he is more familiar to the audience. The longest intimacy could not foretell how he would behave then.