Among those conceptions of the history of science which deal with the formation of theories is the concept of the unity of science. This unity is in turn based on the unity of scientific method, the unity of scientific laws and the unity of the language of science. After a systematic explication of modern approaches, historical conceptions of the unity of the language of science are described and analyzed. To these belong first of all the idea of a mathesis universalis (...) and the so called Leibniz program, which leads to the architecture of a Leibniz world. (shrink)