It is commonly acknowledged that there are three kinds of ju dg ement with different character in pedagogy, i. e. the factual judgement which expla ins the phenomenon of education, the duty judgement that standardizes teachers' behaviour and the judgement that contain the double characters. The proposition t hat teaching embodies the nature of education belongs to the third kind. It funct ions not only as an analysis of education but also a standard of educational beh aviours. Starting from the theory of reflection and dialectic, the thesis analyzed the duality of this proposition.