SOMMARIO: 1. Introduzione. – 2. I presupposti teologici. – 3. Tendenza teocratica, ma visione profana dei fenomeni normativi. – 4. La doppia faccia della secolarizzazione. – 5. Il costituzionalismo (medievale) cristiano. – 6. Le origini del costituzionalismo occidentale. Fra apolitismo radicale … – 7. (segue) … e messianismo temporale e rivoluzione scientifica. – 8. Westfalia (1648): la territorializzazione del diritto religioso. – 9. La nuova religione della perfetta ragione. – 10. Dalla fine della sovranità westfaliana, al secondo dopoguerra … – 11. … (segue) e alla questione islamica di questo secolo.

ABSTRACT: During the long history of the Western Legal System, Christian religion has been playing a key role in defining some of the pillars of modern constitutionalism. This is evident in respect to important constitutional principles like, for example, the notion of “person”, as established in the article 6 of the 1948 Universal Declaration of Human Rights (“Everyone has the right to recognition everywhere as a person before the law”). At the same time, some theological notions of medieval constitutional thought represented the political pedestal of the absolute sovereignty of the State, which is antithetical to the logic of constitutional legal system. With this article, the Author analyses the way some theological notions of Christianity have been “secularized” – and then “codified” – in the Western constitutional States, influencing the pillars of contemporary democracies. This could explain, for example, why the legal instruments carrying out the relationship State-Churches in certain Western democracies do not work very well as they did in the past. In fact, from time to time, these instruments have been able to create the conditions for a proper interaction – an  “overlapping consensus”  – between religious groups and public authorities as well as an acceptable balance between universal principles of Western constitutionalism and ethnic-cultural-religious differences. Nowadays, however, these same instruments seem to fail. Precisely because immigration and today’s multicultural societies see masses of people that come to Western Countries with their religious identities and, sometimes, with a global perspective which complicates the century old tension  between universal principles – launched by the history of the Western constitutionalism – and the current cultural-religious belongings.