Aristotle Rhetoric 3.17.15

[15] He who replies should first state the arguments against the opponent's speech, refuting and answering it by syllogisms, especially if his arguments have met with approval. For as the mind is ill-disposed towards one against whom prejudices have been raised beforehand, it is equally so towards a speech, if the adversary is thought to have spoken well. One must therefore make room in the hearer's mind for the speech one intends to make; and for this purpose you must destroy the impression made by the adversary. Wherefore it is only after having combated all the arguments, or the most important, or those which are plausible, or most easy to refute, that you should substantiate your own case: 20 in this passage the poet has first seized upon the weakest argument.