Are the ideas of the past always wrong? Chronological snobbery

I was reading a book about C. S. Lewis and Tolkien, and came across a discussion of an idea that was common to these two literary giants. That idea is that, just because an idea was held in the past, that, by itself, does not mean that it was false. In fact, it may still be valid, but have been discarded, like the fashions in apparel or hair styles of 40 years ago. The Wikipedia article on Chronological Snobbery gives a quotation from Lewis. In it, he says that we should ask if an idea was ever shown to be wrong, or did it just fade away?

We live too much in the present, and assume that all our ideas are fresh and new, until they quickly fade, into our past.

Read Lewis, and don't practice Chronological Snobbery.