C S Lewis on Reading Old Books

Saw both of these in Piper's Contending for our All (Leicester: IVP, 2006).

Our upbringing and the whole atmosphere of the world we live in make it certain that our main temptation will be that of yielding to winds of doctrine, not that of ignoring them. We are not at all likely to be hidebound: we are very likely indeed to be the slaves of fashion. If one has to choose between reading the new books and reading the old, one must choose the old: not because they are necessarily better but because they contain precisely those truths of which our own age is neglectful. The standard of permanent Christianity must be kept clear in our minds and it is against that standard that we must test all contemporary thought. In fact, we must at all costs not move with the times. We serve One who said, “Heaven and Earth shall move with the times, but my words shall not move with the times” (Matthew 24:35; Mark 13:31; Luke 21:33).
“Christian Apologetics", ” In Essay Collection and Other Short Pieces (London: Harper Collins, 2000) p. 149.

There is a strange idea abroad that in every subject the ancient books should be read only by the professionals, and that the amateur should content himself with the modern books... [Students are directed not to Plato but to books on Plato] - all about "isms" and influences and only once in twelve pages telling him what Plato actually said... But if he only knew, the great man, just because of his greatness, is much more intelligible than his modern commentator...
Now this seems to me topsy-turvy. Naturally, since I myself am a writer, I do not wish the ordinary reader to read no modern books. But if he must read only the new or only the old, I would advise him to read the old. And I would give him this advice precisely because he is an amateur and therefore much less protected than the expert against the dangers of an exclusive contemporary diet. A new book is still on its trial and the amateur is not in a position to judge it. It has to be tested against the great body of Christian thought down the ages, and all its hidden implications (often unsuspected by the author himself) have to be brought to light...
It is a good rule, after reading a new book, never to allow yourself another new one till you have read an old one in between. If that is too much for you, you should at least read one old one to every three new ones.
We all, therefore, need the books that will correct the characteristic mistakes of our own period. And that means the old books... We may be sure that the characteristic blindness of the twentieth century—the blindness about which posterity will ask, "But how could they have thought that?"—lies where we have never suspected it, and concerns something about which there is untroubled agreement between Hitler and President Roosevelt or between Mr. H. G. Wells and Karl Barth. None of us can fully escape this blindness... The only palliative is to keep the clean sea breeze of the centuries blowing through our minds, and this can be done only by reading old books.
Now printed as C S Lewis 'On the Reading of Old Books' in C S Lewis Essay Collection and other Short Pieces, ed. Lesley Walmsley (London: Harper Collins, 2000), pp. 438-440.