Laudator Temporis Acti

Polybius 12.25g.1-3 (tr. Ian Scott-Kilvert):

It is in fact equally impossible for a man who has had no experience of action in the field to write well about military operations as it is for a man who has never engaged in political affairs and their attendant circumstances to write well on those topics. And since the writings of mere book-worms lack both firsthand experience and any vividness of presentation, their work is completely without value for its readers. For if you remove from history the element of practical instruction, what is left is insignificant and without any benefit to them. Again, when writers try to provide details about cities and places without possessing firsthand experience of this kind, the result is bound to be very similar, since they will leave out many things which ought to be mentioned and deal at great length with other details which are not worth the trouble.

Id., 12.25h.5-6:

For this reason the writers of the past believed that historical memoirs should possess such vividness that they would make the reader exclaim whenever the narrative dealt with political events that the author must have taken part in politics and had experience of public affairs; or when he dealt with war that he had known active service and risked his life; or when he turned to domestic matters that he had lived with a wife and brought up children, and similarly with the various other aspects of life. Now this quality can only be found in the writing of those who have played some part in affairs themselves and made this aspect of history their own. Of course it is diffcult to have been personally involved and played an active role in every kind of event, but it is certainly necessary to have had experience of the most important and those of most frequent occurrence.