When they set out to do that, they could not avoid distinguishing certain attributes from others. For they had deemed conception to rest on what they counted as “essential,” and thus had to differentiate between what, in their view, is essential and what is not. They also had to list those attributes in a specific order, since they could not be mentioned in just any sequence. Hence, the attributes they call “essential” supply the material of their artificial definition, while the sequence they prescribe provides its form.

But because this necessarily entails discriminating between things that are identical—or at least very similar—the task proves either impossible or exceedingly hard. They must choose between one attribute and another, labeling one “essential” and not the other even though the two are equal or nearly so. Likewise, they must favor one ordering over another, declaring the first a true definition of the reality and the second not, though both orders are equally—or almost equally—suitable. To seek a distinction between identical things is to pursue what has no reality, and so it is impossible; and to seek it between near-equivalents is painfully difficult. Thus what they require is either unattainable or, if attained, attained only with great hardship. If unattainable, the whole enterprise collapses; and if attainable only with difficulty, it yields no benefit beyond what was already known without it. In the end they are caught between a definition that cannot meet the conditions they themselves set, and one that can meet them yet fails to achieve the intended purpose. On either assumption, the definition they devised is no pathway to conceiving realities for someone who did not already conceive them without the definition—though a definition may still alert the listener and single out the defined object in much the same way that a name does, as will be explained, God willing.

As for their distinction between a “definition” and an “explanation of a name,” its gist is this: once the reality of the thing defined—thereby set apart from other things—is conceived, that reality may be an external existent or a purely mental construct. A definition may be intended merely to clarify what the speaker means by the term, whether or not the meaning he assigns actually exists in the external world; or it may be intended to single out something that truly does exist outside the mind. This is the case whenever anyone interprets or explains another person’s words: he may elucidate the speaker’s intent and purpose, whether or not that intent matches external reality, and it may then become evident that it does, in fact, correspond.