Byzantine philosophy is a way of thinking about the world that was popular in the Byzantine Empire, which was a civilization that lasted in Eastern Europe, in the area of what is now Istanbul, Turkey, from about the 500s to 1450s. Byzantine philosophy was mainly concerned with understanding and explaining the world, and centered around religious beliefs like Christianity and the importance of the emperor. It respected intellectual study and had very strict rules about how to think. One of the main ideas of Byzantine philosophy was that truth was both an empirical observation and a spiritual belief. In other words, they thought that both facts and faith were important.