Laudator Temporis Acti

Hermann Fränkel, Ovid: A Poet between Two Worlds (Berkeley: University of California Press, 1945 = Sather Classical Lectures, 18), p. 1:

As students of classical literature, we cannot expect to have new material wafted onto our desks year in and year out in bountiful quantity; most of the time, we find ourselves handling objects that have been known and used for many centuries. The priceless documents from olden times entrusted to our temporary care remain the same, but each of us will make a fresh effort to comprehend and assess them according to his own lights. There are any number of aspects, all of them equally legitimate, under which a great work of literature may be correctly understood; it is the ephemeral product that allows of one explanation only. On the other hand, any person or generation that is keenly responsive to certain values will inevitably be blind and deaf to certain others, and in the march of literary criticism not every step moves forward. Thus it is only natural that we should frequently be obliged to revise opinions handed down to us.

[....]

However valid a critical judgment may have been in the first place, it will lose some of its cogency with each reiteration, and by the time it has become a truism it has little truth left in it. The reasons for this strange fact seem to be these. Unchallenged perseverance in a belief leads to complacent over-simplification; the complex setting on which the assertion was originally projected gradually fades out, and with its background its justification will be gone; a criticism, in order to be revealing, must stir the mind rather than put it to rest; and we know least about those things we take for granted.