define a theory (to enable or disable a set of rules)
Major Section:  EVENTS

(deftheory interp-theory
             (universal-theory :here)
             (universal-theory 'interp-section)))

General Form: (deftheory name term :doc doc-string)

where name is a new symbolic name (see name), term is a term that when evaluated will produce a theory (see theories), and doc-string is an optional documentation string (see doc-string). Except for the variable world, term must contain no free variables. term is evaluated with world bound to the current world (see world) and the resulting theory is then converted to a runic theory (see theories) and associated with name. Henceforth, this runic theory is returned as the value of the theory expression (theory name).