在整个中世纪时期，只有一个机构接近统一欧洲所有地区，尽管它不是一个政治帝国，而是一个精神政治帝国。这个联盟是天主教会的尝试，它所影响的地缘政治实体被称为“基督教世界”。虽然教会的政治力量和对中世纪欧洲物质文化的影响的确切程度一直并且仍在争论中，但无可否认，它在整个时代对国际事件和个人生活方式产生了重大影响。正因如此，天主教会作为中世纪的决定因素具有有效性。作为西欧最具影响力的宗教，天主教的兴起，建立和最终破裂提供了几个重要的日期，可以作为这个时代的起点和终点。在公元前306年，康斯坦丁被宣布为凯撒，并成为罗马帝国的统治者。在312年，他皈依了基督教，曾经非法的宗教现在变得比其他所有人更受青睐。 （在他去世后，它将成为帝国的官方宗教。）几乎在一夜之间，一个地下邪教成为了“建立”的宗教，迫使曾经激进的基督教哲学家重新思考他们对帝国的态度。 325年，康斯坦丁召集了尼西亚议会，这是天主教会的第一个基督教会议。来自全世界各地的主教的召集是建立有组织的机构的重要一步，这个机构将在未来1200年内产生如此大的影响。这些事件使得325年，或至少在第四世纪初，成为基督教中世纪的可行起点。然而，另一个事件在一些学者的思想中具有同等或更大的重要性：590年加入格雷戈里大帝的教皇宝座。格雷戈里在建立中世纪教皇作为强大的社会政治力量方面发挥了重要作用，许多人认为没有他的努力使天主教会永远不会在中世纪时期取得它所掌握的权力和影响力。
Throughout the Middle Ages, only one institution was close to reunifying all parts of Europe, although it was not a political empire but a spiritual political empire. This alliance is an attempt by the Catholic Church, and the geopolitical entity it affects is called the “Christian World.” Although the political power of the church and the exact extent of its influence on medieval European material culture have been and are still being debated, it is undeniable that it has had a major impact on international events and personal lifestyles throughout the age. For this reason, the Catholic Church is effective as a determining factor in the Middle Ages. As the most influential religion in Western Europe, the rise, establishment and eventual rupture of the Catholic Church provided several important dates that could serve as the starting and ending point of this era. In 306 BC, Constantine was declared Caesar and became the ruler of the Roman Empire. In 312, he converted to Christianity, and the once illegal religion is now more popular than everyone else. (After his death, it will become the official religion of the empire.) Almost overnight, an underground cult became a “established” religion, forcing radical Christian philosophers to rethink their attitude toward the empire. In 325, Constantine convened the Nicaea Parliament, the first Christian church in the Catholic Church. The convening of bishops from all over the world is an important step in the establishment of an organized institution that will have such a large impact in the next 1200 years. These events made 325 years, or at least in the early fourth century, a viable starting point for the Christian Middle Ages. However, another event has equal or greater importance in the minds of some scholars: in 590, he joined the Pope of Gregory the Great. Gregory played an important role in establishing the medieval pope as a powerful socio-political force, and many believed that without his efforts, the Catholic Church would never have the power and influence it had in the Middle Ages.