This thesis undertakes to analyze and elaborate on the interaction relationship,mutual fusion,mutual penetration,mutual conversion,mutual critique,complementation and inseparableness between the rational and irrational and to explore the interrelationship,structure,and mechanism of an integration of irrational factors as well as the value and role that they play in man's understanding,the social and historical development,and man's social practical activities on the basis of man's existence and mankind's spiritual development predicated on the leading role of reason,from the perspectives of integration of the rational and irrational integrating the historical and theoretical,and employing the stances,viewpoints,and methodology of Marxist philosophy,as well as from the multi-dimensional perspectives.This thesis reveals from the dimensions of philosophical and historical evolution the rational and irrational are an integrated,inseparable entity,and that the abstract rational and irrational do not exist. The common inadequacy of traditional rationalism and irrationalism lies in the their ignorance of the fact that man is an "integrated man" with an integration of the rational and irrational. The writer explores the interrelationship,functional mechanism and inner structure of the irrational factors with the irrational as a dimension of integrating entity,laying a foundation for the research on the value of the irrational,elaborates on the value and roles of the irrational in the above areas from the dimensions of the role of theirrational in human cognizance and the role of the irrational in the social and historical development as well as the role of man in practical activities,revealing to man that such irrational factors of man's emotions,needs,inspirations,intuition,faith,will power play an important and irrefutable positive or negative role.An exploration of the value of the irrational is the core of thesis. The objectives of the exploration and elaboration of the value of the irrational in the areas of cognizance,social history,and practical activities are to overcome the partiality of rationalism and irrationalism and to reveal the comprehensiveness and wholeness of man and his activities on the basis of unity of the rational and irrational.