Perhaps all we can say of great acting is that it involves assimilation rather than accumulation, that the performer isn't so much a surrogate as a vessel.
( Perhaps ( ( all ( we ( can ( say ( of ( great acting ) ) ) ) ) ) ( ( is ( that ( it ( ( ( involves ( ( assimilation ( rather than ) ) accumulation ) ) , ) ( that ( ( the performer ) ( ( ( is n't ) ( so much ) ) ( ( a surrogate ) ( as ( a vessel ) ) ) ) ) ) ) ) ) ) . ) ) )
(ROOT (S (ADVP (RB Perhaps)) (NP (NP (DT all)) (SBAR (S (NP (PRP we)) (VP (MD can) (VP (VB say) (PP (IN of) (NP (JJ great) (NN acting)))))))) (VP (VBZ is) (SBAR (IN that) (S (NP (PRP it)) (VP (VBZ involves) (NP (NP (NN assimilation)) (CONJP (RB rather) (IN than)) (NP (NN accumulation))) (, ,) (SBAR (IN that) (S (NP (DT the) (NN performer)) (VP (VBZ is) (RB n't) (ADVP (RB so) (RB much)) (NP (NP (DT a) (NN surrogate)) (PP (IN as) (NP (DT a) (NN vessel))))))))))) (. .)))
A mediocre performer with a lot of roles can still be considered great.
( ( ( A ( mediocre performer ) ) ( with ( ( a lot ) ( of roles ) ) ) ) ( ( ( can still ) ( be ( considered great ) ) ) . ) )
(ROOT (S (NP (NP (DT A) (JJ mediocre) (NN performer)) (PP (IN with) (NP (NP (DT a) (NN lot)) (PP (IN of) (NP (NNS roles)))))) (VP (MD can) (ADVP (RB still)) (VP (VB be) (VP (VBN considered) (S (ADJP (JJ great)))))) (. .)))