  Epistemic logic has inspired other approaches to nonmonotonic logic. Like other modal theories of nonmonotonicity, these use modality to reflect consistency in the object language, and so allow default rules along the lines of DR to be expressed. But instead of consistency, these use ignorance. See  Halpern &amp; Moses 1985  and  Levesque 1987  for variations on this idea. These theories are explained, and compared to other nonmonotonic logics, in  Meyer &amp; van der Hoek 1995.  In more recent work, Levesque’s ideas are systematically presented and applied to the theory of knowledge bases in  Levesque &amp; Lakemeyer 2000.