4.

To say then, that what has once been done rightly must in no respect whatever be changed, is to affirm what is not true. For if the circumstances of time which occasioned anything be changed, true reason in almost all cases demands that what had been in the former circumstances rightly done, be now so altered that, although they say that it is not rightly done if it be changed, truth, on the contrary, protests that it is not rightly done unless it be changed; because, at both times, it will be rightly done if the difference be regulated according to the difference in the times. For just as in the cases of different persons it may happen that, at the same moment, one man may do with impunity what another man may not, because of a difference not in the thing done but in the person who does it, so in the case of one and the same person at different times, that which was duty formerly is not duty now, not because the person is different from his former self, but because the time at which he does it is different.