A Predicate Noun or Adjective after a complementary infinitive takes the case of the subject of the main verb:— fierīque studēbam êius prūdentiā doctior (Lael. 1) , I was eager to become more wise through his wisdom. sciō quam soleās esse occupātus (Fam. 16.21.7) , I know how busy you usually are (are wont to be). brovis esse labōrō, obscūrus fīō ; ( Hor. A. P. 25 ), I struggle to be brief , I become obscure.