It appears to me that the dignity of history also demands such a man.
Plato, as we know, tells us that human affairs will then go well when either philosophers become kings or kings study philosophy,
and I would say that it will be well with history either when men of action undertake to write history,
not as now happens in a perfunctory manner, but when in the belief that this is a most necessary and most noble thing they apply themselves all through their life to it with undivided attention,
or again when would-be authors regard a training in actual affairs as necessary for writing history. Before this be so the errors of historians will never cease.
Timaeus never gave a moment's thought to this, but though he spent all his life in exile in one single place, though he almost seems to have deliberately denied himself any active part in war or politics or any personal experience gained by travel and observation, yet, for some unknown reason, he has acquired the reputation of being a leading author.
That such is the character of Timaeus can easily be shown from his own avowal.
For in the preface to the sixth book he says that some suppose that greater talent, more industry, and more previous training are required for declamatory than for historical writing. Such opinions, he says, formerly incurred Ephorus's disapproval,
but as that writer could give no satisfactory answer to those who held them, he himself attempts to institute a comparison between history and declamatory writing, a most surprising thing to do, firstly in that his statement about Ephorus is false. For Ephorus, while throughout his whole work he is admirable in his phraseology, method, and the originality of his thought, is most eloquent in his digressions and in the expression of his personal judgement, whenever, in fact, he allows himself to enlarge on any subject,
and it so happens that his remarks on the difference between historians and speech-writers are peculiarly charming and convincing.
But Timaeus, in order not to seem to be copying Ephorus, besides making a false statement about him has at the same time condemned all other historians. For dealing with matters, treated by others correctly, at inordinate length, in a confused manner, and in every respect worse, he thinks that not a living soul will notice this.
Walbank Commentary