Before the mid-Edo period, outstanding science of the foreign countries generally were brought to Japan through China in the form of Chinese books, and for this reason, all of the scientific researches of foreign origins were regarded as 'kangaku.'
江戸時代中期以前においては、外国の優れた学術は漢籍の形で中国から入ってくるのが一般的であったため、外来の学術研究は全て「漢学」と考えられてきた。