The purpose of this article is to evaluate the Moist Canons from the point of view of logic, as a system of definitions. We concentrate more specifically on the formal organization of the upper part of the Moist Canons. This method leads us to a globally positive evaluation of the system of definitions but also to the less expected conclusion that a few very basic concepts are undefined and form the background of the Moist concrete, realist, and pragmatic philosophical system: ran, to be so; de, to obtain; ming, illumination; zuo, to initiate; and wei, to act.