Parting shots, by definition, should not be over-prepared. Mine have to do with modest activities and modest messages.

What, for example, do I do in Cambridge if I find myself with some genuinely free time? Mostly, I haunt bookshops, even if for 30 or 40 minutes. This is therapeutic—“retail therapy” one might say.

I have no one favorite shop, but tend to do the equivalent of a pub-crawl—moving slowly place to place, making the rounds. I’m fairly omnivorous. Almost always, I enter with no plans to buy anything. Invariably, I end up with something, and usually far more than even I might have imagined.

Why are bookstores and book browsing so irresistible? Well, there are some reasons, but reasons rarely tell all the story. Nonetheless, when it became clear to me—long ago—that I was likely to remain in academic administration indefinitely, I decided that I could not possibly keep up my scholarly existence, but that I could and would keep up my intellectual existence.

I did this essentially by giving myself permission to read as much and as widely as I wanted in any field, on the theory that all of it would sooner or later be valuable (quite apart from being enjoyable) if I were going to spend the rest of my time thinking about universities and knowledge as a whole, rather than mainly from my own specialized area.

This decision proved to be the right one, at least for me. Browsing through bookshelves can be a mini form of education in itself—one sees, if only through a small window, what’s coming out in many different fields. It’s a bit like reading the Times Literary Supplement, or the London Review, or the New York Review of Books.

Having a library of my own, however, is the real point, as is keeping it well ordered and well stocked. If my books aren’t in order, then I feel that my mind is slightly disheveled—I can’t find much in it. But having the shelves filled in a coherent way keeps my intellectual life, and especially its history, visible and accessible. The library is for me a kind of proxy for an active memory—an index, and a geography that enables me to keep a great deal of what I have read and thought in a form that is alive and ready at hand.

Fortunately, out of all the existing addictions in the world, the one that has bewitched me—book buying—is entirely legal, fairly inexpensive, potentially beneficial, not especially perishable and completely free of calories or deleterious side effects. And, since I have never ventured into the territory of trying to collect rare books, I have been saved yet again from something potentially ruinous.