Few fallacies are more dangerous or easier to fall into than that by which, having read a given book, we assume that we will continue to know its contents permanently, or, having mastered a discipline in the past, we assume that we control it in the present. Philosophically speaking, “to learn” is a verb with no legitimate past tense.Grudin, Time and the Art of Living, page 110
I’m amazed at how quickly I can unlearn a book read last year, let alone years ago. I think this is part of the attraction of a physical library for me: it’s a record of what I’ve read before, without which I would almost certainly forget. See also:
Reading is not just acquainting ourselves with a text or acquiring knowledge; it is also, from its first moments, an inevitable process of forgetting.
Even as I read, I start to forget what I have read, and this process is unavoidable. It extends to the point where it’s as though I haven’t read the book at all, so that in effect I find myself rejoining the ranks of the non-readers, where I should no doubt have remained in the first place. At this point, saying we have read a book becomes essentially a form of metonymy. When it comes to books, we never read more than a portion of greater or lesser length, and that portion is, in the longer or shorter term, condemned to disappear. When we talk about books, then, to ourselves and to others, it would be more accurate to say that we are talking about our approximate recollections of books, arranged as a function of our current circumstances.Bayard, How to Talk About Books You Haven’t Read, page 47
This, of course, is what makes talking about books interesting: we are not talking about books so much as we are talking about ourselves.