1Of the four headings, however, into which we have divided the nature and force of the honourable, the first, which consists in the knowledge of truth, touches human nature most closely. 1For we are all drawn and led to a desire for knowledge and learning, in which we think it a fine thing to excel, while to slip, to err, to be ignorant, to be deceived we consider both bad and shameful. 1In this kind, which is both natural and honourable, two faults must be avoided: one, that we should not take the unknown for the known and rashly assent to it; 1and whoever wishes to escape this fault (and all ought to wish it) will apply both time and care to considering matters.
19The other fault is that some people devote too great zeal and much effort to matters that are obscure and difficult and also unnecessary. 19If these faults are avoided, whatever effort and care is spent on matters honourable and worth knowing will rightly be praised, as in astronomy we have heard of Gaius Sulpicius, in geometry we ourselves have known Sextus Pompeius, many in logic, and more in civil law, all of which arts are concerned with the investigation of truth; 19but to be drawn away from active life by the pursuit of it is contrary to duty. 19For all the praise of virtue lies in action; 19from which, however, there is often a respite, and many opportunities are given for returning to study; 19besides, the activity of the mind, which never rests, can keep us in the pursuit of knowledge even without effort on our part.
19But all thought and movement of the mind will be occupied either in forming plans about things that are honourable and relate to living well and happily, or in the pursuit of science and knowledge. 19And so much for the first source of duty.