a great premise but only a great premise 
(ROOT (NP (NP (DT a) (JJ great) (NN premise)) (CC but) (NP (RB only) (DT a) (JJ great) (NN premise))))
(ROOT (NP (NP (DT ) (JJ ) (NN )) (CC ) (NP (RB ) (DT ) (JJ ) (NN ))))