Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
Sometimes we may pass from quality to definition, as in actions concerned with lunacy, cruelty and offences against the State. In such cases if it is impossible to assert that the acts alleged were right, we are left with such pleas as,
To use bad language to one's wife does not amount to cruelty.Definition is the statement of the fact called in question in appropriate, clear and concise language.
As I have already said, [*](V. x. 55.) it consists mainly in the statement of genus, species, difference and property. For example, if you wish to define a horse (for I will take a familiar example), the genus is animal, the species mortal, the diffrence irrational (since man also is mortal) and the properly neighing. Definition is employed by the orator for a number of different reasons.
For sometimes, though there may be no doubt as to a term, there is a question as to what it includes, or, on the other hand, there may be no doubt about the thing, but no agreement as to the term to be applied to it. When the term is agreed, but the thing doubtful, conjecture may sometimes come into play, as, for instance, in the question,
What is god?
For the man who denies that god is a spirit permeating all things, assuredly asserts that the epithet
divineis falsely applied to his nature, like Epicurus, who gives him a human form and makes him reside in the intermundane space. While both use the same term god, both have to employ conjecture to decide which of the two meanings is consistent with fact.