Regarding the substances that are natural and generable, if the causes are really these and of this number and we have to learn the causes, we must inquire thus, if we are to inquire rightly. But in the case of natural but eternal substances another account must be given.
Naturazko eta generagarri diren substantziei dagokienez horrela ikertu behar dira zuzen ikertu nahi izanez gero, 5) kausak, hain zuzen ere, horiek eta horrenbeste baitira, eta ezagutu behar dira.