 What renders this picture more problematic is rather the difficulties involved in identifying and distinguishing these stages and the corresponding items. Further complications were also generated by the variations in terminology among several authors, and the various criteria of identity and distinctness applied by them in introducing various different notions of identity and distinctness. In fact, many of the great debates of the authors working within this framework can be characterized precisely as disputing the identity or distinctness of the items featured here, or the very criteria of identifying or distinguishing them.