In a friendship, having correct knowledge of one’s friend is necessary and foundational.  For example, let’s say that one has a friend and holds that this friend lives in Houston, works at an aquarium, is unmarried, and graduated from Miami University while in reality this other individual actually lives in Reading, works at an office, is married, and graduated from West Virginia University.  If such a one were to base his interactions with his friend based on the false things he holds about the friend, then this friendship will be stifled.  Additionally, the deeper the friendship is, the more intimate the knowledge the friends will have of each other.