Many a person has held close, throughout their entire lives, two friends that always remained strange to one another, because one of them attracted by virtue of similarity, the other by difference.

Ludwig observes a common social pattern: a person’s closest relationships can be built on opposite principles—one friend is chosen because they mirror the self (shared temperament, values, habits), while another is chosen because they supply what the self lacks (contrast, novelty, complement). The two friends may never truly connect because each is anchored in a different “logic” of attachment and may even represent competing versions of the person’s identity. The remark implies that friendship is not a single category but a set of functions—affirmation and supplementation—and that an individual can live at the intersection of these needs without reconciling them.