For not only in the case of things which have one common notion does the investigation belong to one science, but also in the case of things which are related to one common nature;
Izan ere, gauza bati dagokionaz esaten direnak ez ezik izaera bakar bati dagozkionaz ere aztertzea 15) dagokio zientzia bakar bati, hauek ere, nolabait, gauza bakar bati dagozkiola esaten baita.