Religious liberty was coined by a Roman-era Christian writing from the losing side
The earliest known use of the phrase freedom of religion, libertas religionis, comes from Tertullian, a Christian writer in the Roman world. His case was bold: worship follows conviction, one person's faith neither harms nor helps another's, and forcing belief is no part of religion at all. Empires had wrestled with the question long before.
Today the idea covers the right to hold, teach, practise and observe a faith, alone or with others, and equally the right to hold none. Most nations call it a fundamental human right, and it is written into the International Covenant on Civil and Political Rights, the American and European human rights conventions and the UN Convention on the Rights of the Child. Courts still argue over where it ends, when religious conduct would otherwise break secular law, in cases such as Reynolds v. United States, Wisconsin v. Yoder and S.A.S. v. France.
Around 550 BC Cyrus the Great founded the Achaemenid Empire and adopted a general policy of letting subjects keep their religions, recorded on the Cyrus Cylinder. In the third century BC Ashoka, ruling the Buddhist Maurya Empire, had edicts carved promising freedom of worship; one inscription warns against praising your own creed by running down others. In the thirteenth century Genghis Khan enacted one of the first laws explicitly guaranteeing religious freedom to every faith.
Rome was broadly tolerant, encouraging conquered peoples to keep their gods and accepting Judaism for its antiquity. Christians were the exception, because they refused honours to the imperial cult, until Galerius legalised Christianity in 311. The Edict of Milan then guaranteed religious freedom across the empire, but the Edict of Thessalonica of 380 reversed course and outlawed every religion except Christianity.
Medieval Catholic kingdoms mostly clamped down, and Spain expelled its Jews in 1492. After Granada fell that same year, its Muslims were promised freedom of worship under a treaty, only to face a choice in 1501 between conversion and emigration. Some buildings now stand as reminders of the principle: London's Bevis Marks Synagogue, active since 1701 and the oldest continuously used synagogue in Europe, and the Golden Temple at Amritsar, seen as an emblem of open worship.
Source: Freedom of religion
