Quintilian, and J.S. Watson. Institutes of Oratory.Edited by Lee Honeycutt, 2010. Kindle Electronic Edition. Book VII Chapter 3.
The exact definition of a crime is important to a case (Quintilian VII.3.1). Quintilian sees definition as very similar to the process of conjecture. It serves to make a clear and adequate identification of the subject matter (Quintilian VII.3.3). Quintilian illustrates the fact that one word may refer to several different things, making adequate definition critical. Because of its function, definition is very similar to syllogism (Quintilian VII.3.11). It analyzes the nature of a word or concept to reach a necessarily correct understanding. Quintilian notes that while a clear definition may be used to govern an argument it may not serve to change the opinion of a judge (Quintilian VII.3.14). Since a definition is binding upon those who accept it, Quintilian urges caution in precision (Quintilian VII.3.22). He illustrates various ways in which a definition may be a problem.