(delete-theory [<theory>] [implementation>])
Deletes the specified theory. All included theories will be unincluded. All including theories will be made to uninclude the theory being deleted. Returns T if an appropriate theory was found and deleted, nil otherwise. See also DELETE-THEORY-AND-CHILDREN.
<theory> may be any object acceptable to FIND-THEORY. If unspecified, the current theory is assumed (see IN-THEORY and *CURRENT-THEORY*.)
<implementation> is the name of an implementation, as given to IN-IMPLEMENTATION. It is used to disambiguate the <theory> argument if that theory is given as a symbol.