This is the latin
term for arguing both sides
of an issue and means "on either side". Aristotle
says that only by using this technique will one reach the true state of things, and that the approach is useful for anticipating counter-arguments.
This term is not so much a figure of speech as a general approach to rhetoric, or an overall argumentative strategy. It could also be used within a larger speech, though, in order to exhibit fairness to one's opponents.