1But since I had resolved to write something to you at this time, and much hereafter, I wished above all to begin from that which would be most suited both to your age and to my authority. 1For although many weighty and useful subjects in philosophy have been discussed carefully and fully by philosophers, the teachings and precepts they have handed down about duties seem to have the widest range. 1For no part of life, neither in public nor in private affairs, neither in the forum nor at home, neither if you do something on your own account nor if you make an agreement with another, can be free of duty; and in its observance lies all the honour of life, and in its neglect all the disgrace.
5And this question, indeed, is common to all philosophers; 5for who is there who would dare to call himself a philosopher without handing down any precepts of duty? 5But there are some schools which, by the ends of good and evil that they propose, overturn all duty. 5For he who so lays down the highest good that it has no connection with virtue, and measures it by his own advantage, not by what is honourable, such a man, if he were consistent with himself and were not sometimes overcome by the goodness of his nature, could cultivate neither friendship nor justice nor generosity; 5but a man who judges pain the greatest evil certainly cannot in any way be brave, nor one who declares pleasure the highest good be temperate.
6Although these points are so obvious that the matter needs no discussion, I have nevertheless discussed them elsewhere. 6These schools, then, if they wish to be consistent with themselves, could say nothing about duty, and no firm, stable precepts of duty, joined to nature, can be handed down except by those who say that the honourable is to be sought for its own sake, either alone or above all. 6Thus that teaching belongs properly to the Stoics, the Academics and the Peripatetics, since the views of Aristo, Pyrrho and Erillus have long since been hissed off the stage; 6yet they would have their own right to discuss duty if they had left some choice between things, so that there might be a way of approach to the discovery of duty.
6Accordingly, at this time and in this inquiry, I shall follow chiefly the Stoics, not as a translator, but, as is my custom, I shall draw from their springs according to my own judgement and discretion, as much and in whatever manner shall seem good. 7It seems best, then, since the whole discussion is to be about duty, first to define what duty is; 7and I am surprised that this was passed over by Panaetius. 7For every systematic treatment of any subject that is undertaken by reason ought to start from a definition, so that it may be understood what it is that is being discussed.