According to the author, philosophy of library is a distillation of theories and practices in library science, and popular philosophy of library is a philosophy easily comprehensible to general librarians. Then, the author thinks that library is a place of communications between readers and documents, readers and librarians, readers and readers. It is a social cultural institution and a product of human civilization. Belonging to the social superstructure, it is said to beThe Fourth Social Being. The resea...