Why are Jesuit letters from India, China, and Japan important historical sources?

The letters (cartas) written by Jesuits in India, China, and Japan are considered vital historical sources and human documents because they provide firsthand accounts from some of the first Europeans to visit and describe these regions.1

These documents are important for several reasons:

• Primary Observation: As missionaries, the authors were often among the earliest Europeans to engage with the cultures, societies, and intellectual traditions of Asia, offering unique perspectives that were otherwise unavailable to the Western world at the time.12
• Historical Documentation: Beyond their religious purpose, these letters serve as significant records of the era of discovery and conquest, detailing the experiences of Portuguese travelers and the conditions they encountered in distant lands.1
• Cultural Insight: The correspondence often captured the missionaries' observations on the sophistication and customs of the local populations, such as St. Francis Xavier’s reflections on the Japanese people, which helped shape European understanding of these civilizations.2

By documenting these encounters, the Jesuit letters provide an essential, albeit specific, lens through which historians analyze the early interactions between Portugal and the East.1