( There ( ( is ( ( a ( certain ( natural law ) ) ) ( at work ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBZ is) (NP (NP (DT a) (JJ certain) (JJ natural) (NN law)) (PP (IN at) (NP (NN work))))) (. .)))
There is a certain natural law at work.
(ROOT (S (NP (NP (DT A) (NN statement)) (SBAR (WHNP (WDT that)) (S (VP (VBZ describes) (SBAR (WHNP (WP what)) (S (ADVP (RB always)) (VP (VBZ happens) (PP (IN under) (NP (NP (JJ certain) (NNS conditions)) (PP (IN in) (NP (NN nature)))))))))))) (VP (VBZ is) (ADVP (RB also)) (VP (VBN known) (PP (IN as) (NP (JJ scientific) (NN law))))) (. .)))