Historically, letters have existed from the time of ancient India, ancient Egypt and Sumer, through Rome, Greece and China, up to the present day. During the seventeenth and eighteenth century, letters were used to self-educate. Letters were a way to practice critical reading, self-expressive writing, polemical writing and also exchange ideas with like-minded others. For some people, letters were seen as a written performance. For others, it was not only seen as a performance but also as a way of communication and a method of gaining feedback. Nowadays, letters make up several of the books of the Bible. Archives of correspondence, whether for personal, diplomatic, or business reasons, serve as primary sources for historians. At certain times, the writing of letters has risen to be an art form and a genre of literature, for instance in Byzantine epistolography.[4]