Toleration is a topic that has attracted significant attention in the humanities. Previous historical studies concerning toleration have justified the modern West and the nation state while overusing the term 'toleration' without clarifying its actual meaning in describing the teleology of modernization and the essentialism of nationality based on an analysis of the 'degree' of toleration (how tolerant or intolerant). As a response to this state of the scholarship, this paper attempts to reform the existing understanding by strictly defining the term 'toleration' and by focusing not on the 'degree' but instead on the the 'function' of toleration (the influences of toleration on the relationships of those who tolerated and those who were tolerated). As a case study, this paper deals with the Dutch Republic, which has been referred to as a 'paradise of toleration' since the early modern era, more specifically focusing on the interconfessional relationship between the Reformed and the Catholic congregations in Utrecht during the 1670s. In recent studies concerning toleration in the Dutch Republic, the division of the 'public' and the 'private' has attracted considerable attention. This paper also tentatively hypothesizes that the borderline between the 'public' and the 'private' was drawn between the inside and outside of houses. However, a recent study regarding the French occupation in Utrecht (1672-73), provided only limited information concerning the function of toleration, the behavior of the Catholics, and the process of the reorganization of the public sphere. In order to solve these problems, this paper focuses on the behavior of the Catholics in the public sphere and examines the function of toleration in practice in the political dimension. Through these analyses, this paper attempts to investigate the cause of struggle for the practice of faith, and to clarify the interconfessional relationship of both congregations and the transition of the public sphere. Under the Dutch Republic, the Reformed congregation had the freedom of public practice of faith and the Catholics had the freedom of conscience as their vested right. Catholics, being deprived of the right to practice their faith in public, were relegated to keeping their faith in the schuilkerk (clandestine church), which referred to chapels within houses. In addition, both congregations wished to construct a homogeneous confessional community as a confessionalistic utopia. In other words, in the Dutch Republic, 'toleration as connivance' divided the 'private' from the 'public', constructed a fictional confessionalsitic utopia of the Reformed church in the public sphere, and concealed the hostility of the interconfessional relationship from the public sphere. During the French occupation, Catholics demanded the implementation of their confessionalistic utopia. However, the French army, which was vital for realization of this utopia, transformed the actual situation into one that differed from the utopia sought by the Catholics. Contrary to the Catholics' demand for the exclusive right of the public practice of their faith, the French army granted a 'toleration as limited recognition (type α)' to both congregations. This toleration revealed the hostility of the interconfessional relationship in the public sphere by breaking the single congregation's monopoly on the public practice of faith, so the fiction collapsed. Although the secular authorities of Utrecht requested that both congregations accept 'toleration as civic concord' in order to control the hosility of the interconfessional relationship, their effort had limited effect. After the French evacuation, Utrecht was restored to the Dutch Republic. 'Toleration as limited recognition (type α)' was abandoned and 'toleration as connivance' seemed to reconstruct the fiction of a homogeneous Reformed community in the public sphere as before. However, an influential Catholic priest J. van Neercassel perservered throug