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general::
Phrase(s): play (the) devil’s advocate
Fig. to put forward arguments against or objections to a proposition—which one may actually agree with—purely to test the validity of the proposition. (The devil’s advocate opposes the canonization of a saint in order to prove that the grounds for canonization are sound.) • I agree with your plan. I’m just playing the devil’s advocate so you’ll know what the opposition will say. • Mary offered to play devil’s advocate and argue against our case so that we would find out any flaws in it.
McGrawhill's American Idioms And Phrasal Verbs