forces us to consider the unthinkable , the unacceptable , the unmentionable 
(ROOT (S (VP (VBZ forces) (NP (PRP us)) (S (VP (TO to) (VP (VB consider) (NP (NP (DT the) (JJ unthinkable)) (, ,) (NP (DT the) (JJ unacceptable)) (, ,) (NP (DT the) (JJ unmentionable)))))))))
(ROOT (S (VP (VBZ ) (NP (PRP )) (S (VP (TO ) (VP (VB ) (NP (NP (DT ) (JJ )) (, ) (NP (DT ) (JJ )) (, ) (NP (DT ) (JJ )))))))))