From WordNet (r) 1.6 [wn]:

  dialectic
       adj : of or relating to or employing dialectic; "the dialectical
             method" [syn: {dialectical}]
       n 1: any formal system of reasoning that arrives at the truth by
            the exchange of logical arguments
       2: a contradiction of ideas that serves as the determining
          factor in their interaction; "this situation created the
          inner dialectic of American history"