In Japan Shiro Sugihara is famous both for his studies of history of economic ideas such as Karl Marx, John Stuart Mill, Hajime Kawakami and for his works of library science such as the bibliography of Japanese literature of J.S.Mill.We intend to consider the reason why Sugihara studies history of economic ideas from the bibliographical point of view.In general, "to compare"is an important method of scial sciences.And for Sugihara both"comparison"and"discussion"are important components for his methodology.It is in a context of Mill on Liberty that we realize an important place which Sugihara gives for"comparison"and"discussion".So we are convinced of his interests for an inseparability or a compatibility of his studies of history of economic ideas and his works of library science.