public static Proposition buildFailProposition(Cons tree) {
    { Proposition proposition = Logic.createProposition(Logic.SYM_LOGIC_FAIL, 1);
      Stella_Object argument = Logic.buildProposition(tree.rest.value);

      if (argument == null) {
        return (null);
      }
      (proposition.arguments.theArray)[0] = argument;
      return (proposition);
    }
  }