Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
What is not a property will be a difference: it is, for instance, one thing to be a slave, and another to be in a state of servitude; hence the distinction raised in connexion with persons assigned to their creditors for debt: A slave, if he is manumitted becomes a freedman, but this is not the case with one who is assigned. There are also other points of difference which are dealt with elsewhere. [*](VII. iii. 26. Also III vi. 25.)
Again, the term difference is applied in cases when the genus is divided into species and one species is subdivided. Animal, for instance, is a genus, mortal a species, while terrestrial or biped is a difference: for they are not actually properties, but serve to show
which latter he calls form, from definition and includes them under relation. For example, if a person to whom another man has left all his silver should claim all his silver money as well, he would base his claim upon genus; on the other hand if when a legacy has been left to a married woman holding the position of materfamilias, it should be maintained that the legacy is not due to a woman who never came into the power of her husband, the argument is based on species, since there are two kinds of marriage. [*]( There was the formal marriage per coemptionem, bringing the woman under the power ( in manum )of her husband and giving her the title of materfamilias, and the informal marriage based on cohabitation without involving the wife's coming in manum mariti. ) Cicero [*]( Cic. Top. )