Abstract: Mathematics is not just a methodology of mathematical tools， but also the specification of the “nature of things” from the very beginning. Mathematical metaphysics is not the mathematical subjects or methods in a narrow sense， but a prior “planning” of the “Ta mathemata” facing the world. The reason why mathematics can stipulate the metaphysical “prior” on the “nature of things” is the “pure reason” form of mathematics detached from empirical things. No matter how purely rational the abstract form of mathematics is beyond reality， its root cause should be found in the technical practices of human survival. Under the detached abstract form of mathematics， it reveals the essence of technical planning and constructs the external world， which is also the deep reason why “unnatural” mathematics can be effectively applied in the “natural” scientific research.

Key words: mathematics; metaphysics; pure reason; essence of technology; technical practice