22. In the first book we made our division in such a way as to set in the first place what is virtuous and what is seemly; for all duties are derived from these. In the second place we set what is useful. But as at the start we said that there was a difference between what is virtuous and what is seemly—which one can comprehend more easily than one can explain—so also when we are thinking of what is useful, we have to give considerable thought to what is the more useful. Cic. de Off. II. 3.