Amid the wreckage of the Roman Empire, one governing institution alone remained upright--the Christian Church with its organization for ministering to the spiritual needs of its members. With the conversion of the barbarians to Christianity the governing functions and influence of the Church became more and more important; and it was upon the basis of Church government that political idealism, so long in abeyance, was reawakened. The thinkers who took up the work of Plato and Aristotle on the larger stage of the Holy Roman Empire boldly looked forward to the time when mankind should be united under one government and that government should embody the highest ideals of mankind. Such an ideal seemed indeed to many one of the legacies of the Founder of Christianity. The familiar petition in the Lord's Prayer: _thy kingdom come, thy will be done on earth as it is in heaven_ sounded, in the ears of Dante and Thomas Aquinas and innumerable theologians and canonists, as a prayer and a pledge for the ultimate political unity of mankind on the basis of Christian Law. Such a belief was indeed the bedrock of mediaeval political thought. To devout Christians, brought up in the oecumenical traditions of the Roman Empire, 'every ordering of a human community must appear as a component part of that ordering of the world which exists because God exists, and every earthly group must appear as an organic member of that _Civitas Dei_, that God-State, which comprehends the heavens and the earth.[1] ... Thus the Theory of Human Society must accept the divinely created organization of the Universe as a prototype of the first principles which govern the construction of human communities.... Therefore, in all centuries of the Middle Age, Christendom, which in destiny is identical with Mankind, is set before us as a single, universal Community, founded and governed by God Himself. Mankind is one "mystical body"; it is one single and internally connected "people" or "folk"; it is an all-embracing corporation, which constitutes that Universal Realm, spiritual and temporal, which may be called the Universal Church, or, with equal propriety, the Commonwealth of the Human Race. Therefore, that it may attain its one purpose, it needs One Law and One Government.'[64]