The Collaborative International Dictionary of English v.0.48:

Ideation \I`de*a"tion\, n.
   The faculty or capacity of the mind for forming ideas; the
   exercise of this capacity; the act of the mind by which
   objects of sense are apprehended and retained as objects of
   thought.
   [1913 Webster]

         The whole mass of residua which have been accumulated .
         . . all enter now into the process of ideation. --J. D.
                                                  Morell.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ideation
    n 1: the process of forming and relating ideas