(S (S (NP (BASENP (DT The) (NN idea)) (PP (IN of) (BASENP (NN libertarianism)))) (VP (VBZ is) (SBAR (SBAR (WHADVP (WRB where)) (S (BASENP (NN consent)) (VP (VBZ is) (VP (VBN required) (PP (IN for) (NP (BASENP (DT all) (NNS actions)) (PP (IN between) (BASENP (NNS people))))))))) (CONJP (COMMA ,) (CC and)) (SBAR (IN that) (S (BASENP (DT these) (NNS interactions)) (VP (VBP are) (ADJP (JJ voluntary)))))))) (PERIOD .))