The distinguishing "marks" must not only have an essential relation to knowledge but also be the essential characteristics of the things, and the system of marks devised must conform to the system of nature itself, and merely express this system.
Ezaugarriek ezagutzarekin zerizanezko harremana izateaz gain, gauzen determinatutasun zerizanezkoek eta sistema artifizialak naturaren sistemaren araberakoa izan behar dute, eta hori soilik adierazi behar dute.