Recently we proposed “quantum language" (or,“the linguistic Copenhagen interpretation of quantum mechanics"), which was not only characterized as the metaphysical and linguistic turn of quantum mechanics but also the linguistic turn of
Descartes=Kant epistemology. Namely, quantum language is the scientific final goal of dualistic idealism. It has a great power to describe classical systems as well as quantum systems. Thus, we believe that quantum language is the language in which science is written. The purpose of this preprint is to examine and assert our belief (i.e.,“proposition in quantum language" ⇔“scientific proposition). We believe that it's one of main themes of scientific philosophy to make such language.