is they have a tendency to slip into hokum . 
(ROOT (S (VP (VBZ is) (NP (PRP they)) (VP (VBP have) (NP (DT a) (NN tendency) (S (VP (TO to) (VP (VB slip) (PP (IN into) (NP (NN hokum))))))))) (. .)))
(ROOT (S (VP (VBZ ) (NP (PRP )) (VP (VBP ) (NP (DT ) (NN ) (S (VP (TO ) (VP (VB ) (PP (IN ) (NP (NN ))))))))) (. )))