The Collaborative International Dictionary of English v.0.48:

Casuist \Cas"u*ist\, v. i.
   To play the casuist. --Milton.
   [1913 Webster] Casuistic

The Collaborative International Dictionary of English v.0.48:

Casuist \Cas"u*ist\, n. [L. casus fall, case; cf. F. casuiste.
   See Casual.]
   One who is skilled in, or given to, casuistry.
   [1913 Webster]

         The judment of any casuist or learned divine concerning
         the state of a man's soul, is not sufficient to give
         him confidence.                          --South.
   [1913 Webster]

WordNet (r) 3.0 (2006):

casuist
    n 1: someone whose reasoning is subtle and often specious [syn:
         casuist, sophist]