We expect from book 1 that Aristotle will begin with the general account or definition of soul (see 402a7–10). Since soul is the subject matter of the present investigation, the definition of soul will provide the primary principle. Unlike most of his predecessors who concentrated exclusively on animal or even merely human soul, Aristotle aims for an account that applies as widely as possible, that covers every instance of ensouled being. He thus makes a decision regarding questions raised back in 402b3–10 about how wide the definition should be and what should be the order of the inquiry. His is not merely a general account of soul but the most general or common account. An advantage of such general definition is to keep the project at its proper level. Neither will Aristotle go below the level of the soul in an attempt to reduce soul to nonsoul; nor will he go above soul generally to speak only of mind. Since the definition is so general, applying to the various sorts of soul even beyond a genus such as animal, it will not be definition in the strictest sense (Metaphysics vii; 4.1030a11–12 claims that strictly only the species of a genus has an essence and definition). Nevertheless, the worth of this definition, besides the clarity it gives to soul as principle of body and the living being, is the platform it provides for accounts of the soul's faculties occupying the rest of the treatise.