Although the transitions were gradual, and exact dates for the demarcation of the Middle Ages are misleading, convention often places the beginning of the period between the death of the Roman emperor Theodosius I in 395 and the fall of Rome to the Visigoths in 410. The Dark Ages, formerly a designation for the entire period of the Middle Ages, now refers usually to the period c.450–750, also known as the Early Middle Ages. In fact, the term Dark Ages may be more a judgment on the lack of sources for evaluating the period than on the significance of events that transpired.

Medieval Europe was far from unified; it was a large geographical region divided into smaller and culturally diverse political units that were never totally dominated by any one authority. With the collapse of the Roman Empire, Christianity became the standard-bearer of Western civilization. The papacy gradually gained secular authority; monastic communities, generally adhering to the Rule of St. Benedict, had the effect of preserving antique learning; and missionaries, sent to convert the Germans and other tribes, spread Latin civilization.

By the 8th cent. culture centered on Christianity had been established; it incorporated both Latin traditions and German institutions, such as Germanic laws. The far-flung empire created by Charlemagne illustrated this fusion. However, the empire's fragile central authority was shattered by a new wave of invasions, notably those of the Vikings and Magyars.

Feudalism, with the manorial system (see also tenure) as its agricultural base, became the typical social and political organization of Europe. The new framework gained stability from the 11th cent., as the invaders became Christian and settled and as prosperity was created by agricultural innovations, increasing productivity, and population expansion.

As Europe entered the period known as the High Middle Ages, the church became the universal and unifying institution. While some independence from feudal rule was gained by the rising towns (see commune, in medieval history), their system of guilds perpetuated the Christian and medieval spirit of economic life, which stressed the collective entity, disapproved of unregulated competition, and minimized the profit motive. Strong popes, notably Gregory VII, worked for a reinvigorated Europe guided by a centralized church, a goal virtually realized under Innocent III.

Militant religious zeal was expressed in the Crusades, which also stemmed from the growing strength of Europe. Security and prosperity stimulated intellectual life, newly centered in burgeoning universities (see colleges and universities), which developed under the auspices of the church. From the Crusades and other sources came contact with Arab culture, which had preserved works of Greek authors whose writings had not survived in Europe. Philosophy, science, and mathematics from the Classical and Hellenistic periods were assimilated into the tenets of the Christian faith and the prevailing philosophy of scholasticism; Aristotle, long associated with heresy, was adapted by St. Thomas Aquinas to Christian doctrine.

Christian values pervaded scholarship and literature, especially Medieval Latin literature, but Provençal literature also reflected Arab influence, and other flourishing medieval literatures, including German literature, Old Norse literature, and Middle English literature, incorporated the materials of pre-Christian traditions. The complex currents, vitality, and religious fervor of medieval culture are evident in the classics of Dante and Chaucer. Gothic architecture developed most notably in the 12th cent., against a background of the cultural and economic ascendancy of Western Europe.

The transition from the medieval to the modern world was foreshadowed by economic expansion, political centralization, and secularization. A money economy weakened serfdom, and an inquiring spirit stimulated the age of exploration. Banking, the bourgeois class, and secular ideals flourished in the growing towns and lent support to the expanding monarchies. The church was weakened by internal conflicts as well as by quarrels between church and state. As feudal strength was sapped, notably by the the Hundred Years War and the Wars of the Roses, there emerged in France and England the modern nation state. A forerunner of intellectual modernity was the new humanism of the Renaissance. Finally, the great medieval unity of Christianity was shattered by the religious theories that culminated in the Protestant Reformation.