def send(self, message, arguments=None):
        """Send a message to the Instance.

        Message arguments must be provided as a string.

        """
        output = clips.data.DataObject(self._env)
        instance = clips.data.DataObject(
            self._env, dtype=CLIPSType.INSTANCE_ADDRESS)
        instance.value = self._ist

        args = arguments.encode() if arguments is not None else ffi.NULL

        lib.EnvSend(
            self._env, instance.byref, message.encode(), args, output.byref)

        return output.value