* @return Stella_Object
   */
  public static Stella_Object unassert(Stella_Object proposition) {
    { Cons parsedprops = Logic.updateProposition(proposition, Logic.KWD_CONCEIVE);
      Cons result = Stella.NIL;

      if (parsedprops != null) {
        { Proposition prop = null;
          Cons iter000 = parsedprops;
          Cons collect000 = null;

          for (;!(iter000 == Stella.NIL); iter000 = iter000.rest) {
            prop = ((Proposition)(iter000.value));
            if (prop.kind == Logic.KWD_NOT) {
              prop = ((Proposition)((prop.arguments.theArray)[0]));
            }
            Proposition.unassertProposition(prop);
            if (collect000 == null) {
              {
                collect000 = Cons.cons(prop, Stella.NIL);
                if (result == Stella.NIL) {
                  result = collect000;
                }
                else {
                  Cons.addConsToEndOfConsList(result, collect000);
                }
              }
            }
            else {
              {
                collect000.rest = Cons.cons(prop, Stella.NIL);
                collect000 = collect000.rest;
              }
            }
          }
        }
      }
      return (((result.length() > 1) ? result : result.value));
    }
  }