Aasen's work is based on the idea that Norwegian dialects had a common structure that made them a separate language alongside Danish and Swedish. The central point for Aasen therefore became to find and show the structural dependencies between the dialects. In order to abstract this structure from the variety of dialects, he developed some basic criteria, which he called the most perfect form. He defined this form as the one that best showed the connection to related words, with similar words, and with the forms in Old Norwegian. No single dialect had all the "perfect forms"; each dialect had preserved different aspects and parts of the language. Through such a systematic approach, Aasen believed one could arrive at a uniting expression for all Norwegian dialects, what he called the fundamental dialect; Einar Haugen called it Proto-Norwegian.
Aasen's work is based on the idea that Norwegian dialects had a common structure that made them a separate language alongside Danish and Swedish. The central point for Aasen therefore became to find and show the structural dependencies between the dialects. In order to abstract this structure from the variety of dialects, he developed some basic criteria, which he called the most perfect form. He defined this form as the one that best showed the connection to related words, with similar words, and with the forms in Old Norwegian. No single dialect had all the "perfect forms"; each dialect had preserved different aspects and parts of the language. Through such a systematic approach, Aasen believed one could arrive at a uniting expression for all Norwegian dialects, what he called the fundamental dialect; Einar Haugen called it Proto-Norwegian.