The broadest, most genre-like classification of a story's structural nature
The possible places where problems can exist can be divided into four areas, and we call these areas the four Classes. The Classes are separated by distinctions between inner and outer states and processes. Situation (Universe) and Activities (Physics) represent external states and processes respectively, and Fixed Attitudes (Mind) and Manipulation (Psychology) represent internal states and processes respectively. Though Classes have the same names as Throughlines, they represent only a structural ordering of semantic terms and are not the same as Throughlines which are more dynamic story points created by matching a Class with one of the four throughlines.