Definition
The Reformation was a religious revolution in 16th-century Western Europe that broke the long monopoly of the Roman Catholic Church and divided Christianity into competing branches. It is usually dated from 1517, when the monk Martin Luther publicly challenged Church practices.
What began as a call to reform abuses within the Church grew into a permanent split. New Protestant churches rejected the authority of the pope, and the Catholic Church responded with its own reforms, a phase known as the Counter-Reformation.
Why it matters
How it works
The Reformation worked through ideas, technology, and politics together. Reformers preached and published their case; the printing press carried it to a wide audience; and local rulers chose sides, often for political as much as spiritual reasons. A prince who adopted Protestantism gained independence from Rome and frequently control of Church lands and revenue.
Once started, the split could not be reversed by debate alone. Differences in doctrine hardened into separate institutions, and the resulting patchwork of faiths set the stage for more than a century of religious conflict.