Book 7
2.9
For at times it is convenient merely to enquire whether one particular term is applicable to a given thing, as in the question whether an act committed in a brothel is adultery. If we deny that it is adultery, there is no need to state what it should be called, since we have given a total denial to the charge. Secondly, there are occasions when the question is which of two terms is to be applied to a thing, as in the question whether an act is theft or sacrilege. It may be sufficient for the defence that it is not sacrilege, but it is still necessary to show what else it is, and therefore we must define both.
2.10
Thirdly, there are times when the question concerns things which are different in species, and we ask whether two different things are to be called by the same name, in spite of the fact that each has a special name of its own: for example, is tile same name applicable both to a love-potion and a poison? cp. VIII. V. 31. But in all disputes of this kind the question is whether one thing is another thing as well, since the name in doubt does without question apply to something else. It is sacrilege to steal a sacred object from a temple; is it also sacrilege to steal private property from a temple? It is adultery to lie with another man's wile in one's own house; is it adultery to do so in a brothel? It is tyrannicide to slay a tyrant; is it tyrannicide to force him to slay himself?
