But even without them, he would certainly have understood that the attacks on the World Trade Center would already have unfolded, given Flight 93's tardy departure from Newark.
( But ( ( even ( without them ) ) ( , ( he ( ( ( ( ( would certainly ) ( have ( understood ( that ( ( ( the attacks ) ( on ( the ( World ( Trade Center ) ) ) ) ) ( ( would already ) ( have unfolded ) ) ) ) ) ) ) , ) ( given ( ( ( Flight ( 93 's ) ) ( tardy departure ) ) ( from Newark ) ) ) ) . ) ) ) ) )
(ROOT (S (CC But) (PP (RB even) (IN without) (NP (PRP them))) (, ,) (NP (PRP he)) (VP (MD would) (ADVP (RB certainly)) (VP (VB have) (VP (VBN understood) (SBAR (IN that) (S (NP (NP (DT the) (NNS attacks)) (PP (IN on) (NP (DT the) (NNP World) (NNP Trade) (NNP Center)))) (VP (MD would) (ADVP (RB already)) (VP (VB have) (VP (VBD unfolded))))))))) (, ,) (PP (VBN given) (NP (NP (NP (NNP Flight) (CD 93) (POS 's)) (ADJP (JJ tardy)) (NN departure)) (PP (IN from) (NP (NNP Newark))))) (. .)))
He knew that the attacks on the World Trade Center would have always happened regardless of anyone's efforts or lack thereof.
( He ( ( ( ( knew ( that ( ( ( the attacks ) ( on ( the ( World ( Trade Center ) ) ) ) ) ( would ( ( have always ) ( happened ( regardless ( of ( ( anyone 's ) efforts ) ) ) ) ) ) ) ) ) or ) ( lack thereof ) ) . ) )
(ROOT (S (NP (PRP He)) (VP (VP (VBD knew) (SBAR (IN that) (S (NP (NP (DT the) (NNS attacks)) (PP (IN on) (NP (DT the) (NNP World) (NNP Trade) (NNP Center)))) (VP (MD would) (VP (VB have) (ADVP (RB always)) (VP (VBN happened) (ADVP (RB regardless) (PP (IN of) (NP (NP (NN anyone) (POS 's)) (NNS efforts)))))))))) (CC or) (VP (VBP lack) (ADVP (RB thereof)))) (. .)))