Religious tolerance is an issue extremely present in the life of humanity. Appeal to tolerance came out of the crisis of Reformation that was subjected to the turmoil of religious wars. Realization of the Protestant ways of tolerance showed its weak points by instability of internal fractions, but also by unequal reference to the old Roman-Catholic confession, or to the new radical forms of Protestantism. Europe of the 18th century needed to escape the whirl of intolerance exercised in the previous centuries. Similarly, this also meant abandonment of the Church in favour of state, and implicitly a clarification of the Church’s relation with the state. The Church (Protestant and Roman Catholic) lost its allies and political supporters, yet still preserving the Orthodoxy of previous centuries. Secularization of the Church and evolution of the society towards realization of tolerant public conscience became more and more evident. Yet, the necessity of tacit tolerance did not produce a de iure declaration of tolerance, only in isolated situations, as in Transylvania (1568) and Poland. In Bohemia, Hungary and Principality of Transylvania understanding the idea of tolerance was primarily connected by the relation of Catholicism with Protestantism and implicitly from the political-religious influence of the House of Habsburg over territories belonging to the crown. Tolerance was stopped in west by: parliamentary decisions Act of Tolerance, England, 1689, Edict of Tolerance from France 1787, Edict of Tolerance from theHapsburg Empire 1781-82. Tolerance became implicitly also a historical issue of philosophy and theology. Tolerance of the Church became also an external issue of the relationship between the state and religious community. In addition, the issue of tolerance appeared as an aspect of laic authority manifestation and obedience requested by alliance state-church. Concordia or reciprocal tolerance was the term by which Europe tried to adjust its turbulent confessional life. By Concordie was wished a sort of Respublica Christiana of monolithic type. The conservatory Catholic reaction referring to confessional diversity aligned with the idea of haereticis non est servanda fides. Tolerance was widely debated in the 18th century. Four leading personalities: John Locke, Pierre Bayle, Voltaire and Rousseau thoroughly preoccupied with defining the term and putting it into practice. At the same time, Jurieu promoted the idea of mutual tolerance (“mutual pact”). In 1757 the issue of tolerance was not yet clearly defined. Distinct notions were under discussion: ecclesiastical tolerance (religious, theological) and the civil one. Different opinions on tolerance tried to influence political life. Diverse writings debated the subject: John Locke, A Letter Concerning Toleration (1667), Of theDifferencebetweenCiviland Ecclesiastical Power (1674), Voltaire, Treatise on Tolerance (1763). Two Voltairian cases played an important role within the evolution of the idea of tolerance. The first case is connected to Helvetic Geneva, which once was the Protestant model city of Jean Calvin. Jean Calvin did not allow disobedience from his Orthodox Protestant principles. He considered the idea of freedom of conscience a novelty, an idea that could not be applied: a “tragic liberty”, as “sects” was gaining ground. The moment of Protestant tolerance took a bad turn by judgement and then burning alive of Michael Servet (1509-1553).In the 18th century, Voltaire appealed to the moment of burning at the stake of Servet as the major fault that Reformation produced, affecting the idea of tolerance. The idea was previously valorised by Sébastien Castellion (1515-1563), a French humanist. Voltaire preoccupied obsessively to do a “business” out of incriminating rapports of Servet with Calvin, by this denouncing Protestant intolerance. Geneva was a tolerant city, due especially to presence of Rousseau and Voltaire, by which expectation of denouncing burning at the stake of Servet became the paradigm of European tolerance. The idea of tolerance enforced especially because of Calas case which became known due to Voltaire, who with this occasion created his Treatise on Tolerance. By Voltaire’s intervention, Calas case became known as the catalyst of the national conscience of the French, this starting a real crusade against religious fanatics represented by the infamy of the Old Regime, which judged and killed without being guilty the Protestant merchant Calas. The philosopher became the defendant of Calas the Calvinist merchant from Toulouse. Together with Rousseau they revealed and internationalized the subject, by which intensity of arguments used in the debate on tolerance was memorable. Through Voltaire, the idea of tolerance, acclaimed and made international by Calas case, became a symbol of liberty of conscience of man, idea characteristic to the Age of Enlightenment. After long turmoil and hesitations, the illuminist idea of civil and religious tolerance was born due to these cases, between 1760 and 1785.