Conceiving what is being reported—without blind imitation of the reporter and without simply accepting his statement in matters that are equally accessible to both reporter and hearer—does not belong to the category of reporting on unseen realities.

Fourth aspect: Knowing the defined object depends solely on knowing the thing meant and its very name.

Fourthly, they proceed to define a thing by means of the attributes they call “essential,” referring to them as the parts of the definition, the parts of the quiddity, the elements that constitute it, those included within it, and the like.

If the listener does not already know that the defined object is characterized by those attributes, it is impossible for him to conceive it; and if he does know that the object is so characterized, he has conceived it without the definition. Hence, under either of the two contrary suppositions, he does not acquire the conception through the definition itself—and this is clear.

Take the statement, “Man is the rational animal.” If the hearer had no prior knowledge of what “man” is, he would merely form a conception of the referent of “rational animal” without realizing that it is man; he would still need to learn of this linkage. If he had not yet conceived the referent of “rational animal,” he would require two things: first, to conceive that referent, and second, to know the linkage just mentioned. And if he already knew these matters, then he had formed a conception of man without the definition.

A definition may nonetheless serve as a prompt: indeed, a definition can draw one’s attention to the object defined just as a name does. The mind may be heedless of a thing, but when it hears either the name or the definition, it turns toward the thing indicated and conceives it. In that case, the benefit of the definition is of the same kind as the benefit of the name—namely, to distinguish the defined object from what is other than it. This is the correct understanding.