Friendship, as a unique form of social relationship, establishes a particular union among individual human beings which allows them to overcome diverse boundaries between individual subjects. Age, gender or cultural differences do not necessarily constitute an obstacle for establishing friendship and as a social phenomenon, it might even include the potential to exist independently of space and time. This analysis in the interface of social science and phenomenology focuses on the principles of construction and constitution of this specific form of (...) human encounter. In a “parallel action,” the perspective of social science focuses on concrete socio-historical constructions of friendship in different time periods. These findings are confronted with the description of principles of the subjective constitution of the phenomenon of “friendship” from a phenomenological perspective. The point of reference for the study is the real type of the symbolically established and excessively idealized form of friendship intended for eternity which was especially popular in eighteenth century Germany. Analogous to the method of phenomenological reduction, three different levels of protosociological reduction are developed for the exploration of the unique social phenomenon of friendship. (shrink)