Medieval religious pluralism was impossible because one God implied one true religion

Evidence

We live in an age where ecumenism, dialogue, and tolerance are often evoked (if not as often practiced) in relations between mainstream religious groups. We define Islam and Christianity as two distinct and valid “religions” among many. In many countries, the choice of religion is (at least in theory) a matter of personal choice, with different religions considered equal before a lay state. Such a perspective was not possible in the Middle Ages. For Muslims, Christians, and Jews of the Middle Ages, there could be only one true “religion,” just as there was only one God. Rival faiths were at best imperfect expressions of the true religion, at worst diabolically inspired error. There was no “lay” state; as each ruler claimed to uphold God’s law, each saw God as the source of his authority over his subjects. One was born into a religious community, and one’s community determined one’s legal status: Jews, Christians, and Muslims had separate, segregated legal and judicial systems, whether they lived in Baghdad or Barcelona. — John V. Tolan, Saracens, 49

Categorization

• DEFINE: Clarifies how the modern concept of ‘religion’ as one of many valid options is a modern category that did not exist in the medieval world.
• XREF: connects to: Medieval thinkers saw all faiths as destined for eventual reunion in one church