著作權法旨在保護著作人私權，調和社會公益，並促進整體文化發展。但從圖書 館事業觀點而言，由於著作權是一種獨占行為，惟有符合合理使用規定方得免除館方法律責 任，合理使用係不確定法律概念，其為圖書館運作的安全瓣，本文即針對著作權法上之一切 不確定法律概念進行剖析，俾使圖書館同道得在著作權法衝擊下有逃生的機會。

　　　　　The major purpose of the Copyright Law is for protecting the right of the authors, mediating the public interest of the community and promoting the cultural development. However, from the viewpoints of the librarianship, the application of Copyright Law is monopoly behavior. Accordingly, the stipulation of fair use not only can get rid of the sanction but also become the safety valve of library operation. Fair use is an unbestimmter Rechtsbegriff. This article will examine all unbestimmter Rechtsbegriff in copyright law in order to find and exodus outlet for librarians.