Defining a German nation based on internal characteristics presented difficulties. Since the start of the Reformation in the 16th century, the German lands had been divided between Catholics and Lutherans and linguistic diversity was large as well. Today, the Swabian, Bavarian, Saxon and Cologne dialects in their most pure forms are estimated to be 40% mutually intelligible with more modern Standard German, meaning that in a conversation between any native speakers of any of these dialects and a person who speaks only standard German, the latter will be able to understand slightly less than half of what is being said without any prior knowledge of the dialect, a situation which is likely to have been similar or greater in the 19th century.[4]