text: For the present, however, we are seeking the primary idea of genus, on which the others, the different species, depend, which is the source of all classification, the term under which universal ideas are embraced. And the idea of genus will be reached if we begin to reckon back from particulars; for in this way we shall be conducted back to the primary notion. Now "man" is a species, as Aristotle says; so is "horse," or "dog." We must therefore discover some common bond for all these terms, one which embraces them and holds them subordinate to itself. And what is this? It is "animal." And so there begins to be a genus "animal," including all these terms, "man," "horse," and "dog." But there are certain things which have life (anima) and yet are not "animals." For it is agreed that plants and trees possess life, and that is why we speak of them as living and dying. Therefore the term "living things" will occupy a still higher place, because both animals and plants are included in this category. Certain objects, however, lack life, – such as rocks. There will therefore be another term to take precedence over "living things," and that is "substance." I shall classify "substance" by saying that all substances are either animate or inanimate. But there is still something superior to "substance"; for we speak of certain things as possessing substance, and certain things as lacking substance. What, then, will be the term from which these things are derived? It is that to which we lately gave an inappropriate name, "that which exists." For by using this term they will be divided into species, so that we can say: that which exists either possesses, or lacks, substance.