From the beginning of16th century, after more than 400 years of struggle and development, to the end of19th century, scientific knowledge (mainly natural science, science and technology and humanities) gradually matured, eventually replacing metaphysics and theology and becoming the dominant curriculum in schools. At this time, knowledge reveals the "essence" of the objective world, which is expressed through special concepts, categories, symbols and propositions. Mathematical language and observation proposition are its basic forms, so knowledge is objective, definite and empirical. Scientists or researchers who master this special language and skills become respected intellectuals, and mastering this knowledge is considered as "not afraid to travel all over the world".