Institutio Oratoria

To these they add property and difference. Properties serve to establish definitions, differences to overthrow them. A property is that which happens to one particular object and that alone; speech and laughter for instance are properties of man. Or it may be something specially belonging to an object, but not to it alone; heating for instance is a property of fire. The same thing may also have a number of properties: light and heat are both properties of fire. Consequently, the omission of any property in a definition will impair it, but the introduction of a property, whatever it may be, will not necessarily establish a definition.

We have, however, often to consider what is a property of some given object; for example, if it should be asserted, on the ground of etymology, that the peculiar property of a tyrannicide is to kill tyrants, we should deny it: for an executioner is not ipso facto a tyrannicide, if he executes a tyrant who has been delivered to him for the purpose, nor again is he a tyrannicide who kills a tyrant unwittingly or against his will.

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. )

further shows that definition is assisted by division, which he distinguishes from partition, making the latter the dissection of a whole into its parts and the former the division of a genus into its forms or species. The number of parts he regards as being uncertain, as for instance the elements of which a state consists; the forms or species are, however, certain, as for instance the number of forms of government, which we are told are three, democracy, oligarchy, and monarchy. It is true that he does not use these illustrations,

since, as he was writing to Trebatius, [*]( A famous lawyer, cp. III. xi. 18. v. 17. ) he preferred to draw his examples from law. I have chosen my illustrations as being more obvious. Properties have relation to questions of fact as well; for instance, it is the property of a good man to act rightly, of an angry man to be violent in speech or action, and consequently we believe that such acts are committed by persons of the appropriate character, or

In a similar way division is valuable both for proof and refutation. For proof, it is sometimes enough to establish one thing.

To be a citizen, a man must either have been born or made such.

he was neither born nor made a citizen.