contrarium

1. Juxtaposing two opposing statements (antithesis) in such a way as to prove the one from the other. More generally, a composition of opposites (antitheton).
Like other Figures of Opposition, contrarium can at times seem to emphasize a lexical pattern and sometimes the semantic or argumentative content. The Ad Herennium author refers to contrarium as a figure of diction (perhaps because of the opposition and frequent parallelism of such statements when expressed concisely). However, as Quintilian notes , contrarium is more properly understood as a method of argumentation (Topic of Invention: Contraries). (Silva Rhetoricae)

2. (Quintilian deems this more a method of argument than a figure of diction): reasoning by contraries; implying the answer to a question by stating an opposing position. (Garret Epp)

3. If a mode of expression both easy and adorned is desired, set aside all the techniques of the dignified style and have recourse to means that are simple, but of a simplicity that does not shock the ear by its rudeness. Here are the rhetorical colours with which to adorn your style: (Vinsauf)

1. Are we afraid to fight those on the plains whom we have hurled down from the hills? (Silva Rhetoricae)

2. For how sholden they love togidre in the peyne of helle, whan they hated hated ech of hem oother in the prosperitee of this lyf? (ParsT 203 qtd. in Garret Epp)

3. But since that man was a slave, shall we enjoy freedom? If he who was strong in great virtue did not resist the foe, how shall we who are frail resist? (Vinsauf)