In 1931, Walter Benjamin wrote a brief essay entitled "Unpacking My Library: A Talk about Book Collecting." In it, he narrates the experience of pulling the many volumes of his personal library out of the crates in which they had been inaccessibly stored for the previous two years. One by one, he describes reencountering familiar texts that stood in his mind not just for the far-flung intellectual passions of their owner, but also for the autobiographical journeys that had led him to discover them on the vividly remembered shelves of obscure bookshops in remote corners of Naples and Munich and Paris and many other cities. Benjamin's particular theoretical position requires him to admit that his intense affection for these books represents a kind fetishism that he is at pains to critique, but he is too honest not to embrace it at the same time as being fundamental to his sense of self. "Every passion," he writes, "borders on the chaotic, but the collector's passion borders on the chaos of memories."

For all of us who love books, which I assume includes most of my fellow historians, Benjamin describes an essential truth about the scholarly life. In our efforts to understand the past, we trace a serendipitous journey from document to document, moment to moment, place to place, in which the books we read (like those we write) become milestones in our emerging sense not just of our subjects, but of our selves. Every major research project involves the careful collecting of sources and interpretations—the threads we hope to weave into tapestries—which we assemble into the stories we ourselves tell. Having searched and found the sources that become our raw materials, we make them our own by forging new connections among them in our notes and in our minds, just as the books emerging from Benjamin's crates found new order and meaning on his shelves. Possessing things in this way involves much more than just physical property, which is why Benjamin can say of the book collector that "ownership is the most intimate relationship that one can have to objects. Not that they come alive in him; it is he who lives in them. So I have erected one of his dwellings, with books as the building stones."

I linger on these volumes from Walter Benjamin's library because they can serve as symbols of the relationships between books and readers that we have not yet fully succeeded in reproducing in the digital world. Indeed, I would go further: it is precisely this collecting of carefully curated, intricately structured, lovingly tended personal libraries—so crucial to the practice of history—that is becoming more challenging as texts that once lived on physical pages bound between the covers of physical books are transformed into virtual e-texts floating ethereally among the virtual shelves of virtual libraries. Again, I am not mainly talking about physical ownership here, though it is no accident that Benjamin's memories were so powerfully triggered by his books as physical objects. I'm concerned instead about metaphorical book collections, the libraries we assemble in our minds in something akin to the rooms of a memory palace—the Roman method of loci—in which texts and ideas gain meaning in relationship to each other by virtue of the mental architecture we create to hold them. It is these mnemonic relationships in our mental libraries that enable us to keep Benjamin's "chaos of memories" at bay. More to the point, it is these relationships we use to write history. At some very deep level, they are stuff of which history is made.

Two features of the digital revolution put this project of building personal libraries—whether physical or mental—at risk. One is the extraordinary new power of search, which makes it possible to rummage the Web for the most arcane information and generally expect to find it with a speed and facility that were inconceivable just two decades ago. This ease in finding information means that even novices can now confidently locate bits of knowledge which only the most skilled scholars would have known how to find in the past, and then only after many years of study.

These new capabilities are in many ways miraculous, and we have all benefited from what Google and other search engines now make possible. But like all innovations, they come at a price. Information so gained is ripped from its original contexts. The very speed with which we find it tempts us not to recognize the work required truly to understand those contexts with all their meanings and ramifications. Furthermore, the power of search means we no longer need nearly so much of the mental architecture without which we couldn't even have found such information in the past, let alone made sense of it. We simply type a few words into the search box, extract the fragment we think we need, and hurry on to the next scrap. Just as the printed book diminished the need for memory palaces, so Google diminishes the need to remember anything but the simplest search strategies. What this means for a discipline like history that is all about context it is too soon to tell.

But there is another feature of the digital realm that poses still subtler challenges. The Roman invention of the multi-paged codex as a replacement for the far more ancient scroll represented an informational revolution that few of us now appreciate. As anyone who has watched the ritual turning of the Torah will understand, finding a single Biblical verse on a scroll is remarkably time-consuming. Finding it in a codex, on the other hand, is as simple as ruffling pages with one's thumb to find in few seconds what would take minutes on a scroll. Although no Roman would have said it this way, the codex remains one of the most powerful random-access devices humanity has yet devised.

Can physical books come close to competing with computers when it comes to search? Of course not. But when one wants to relocate a piece of information in a particular context, and when one remembers that context better than the information itself, then it can be surprisingly difficult for search alone to recover what one wants. What few of us recognize is that computer interfaces have for the most part retreated from the codex back toward the scroll. When we avail ourselves of the astonishing powers of Google, our "search result" comes back to us in the form of a list through which we must slowly—scroll. This is equally true of word processor texts and e-books. When we highlight or make notes in an e-reader and need to find our own annotations again, we do so via a laborious process of search which generates a long list through which we must scroll (often with the most woefully inadequate snippets as our only context) in the hope of relocating what we ourselves wrote. The same annotation or underlining that often took seconds to find in a physical codex can take minutes to relocate using the slow, context-stripping tools thus far available on e-book readers.

This problem of the scroll as a universal metaphor for accessing information is only compounded as we move from the individual text to the virtual library which any scholar must create when working on a large project—or when constructing the metaphorical library of a lifetime. As I sit writing this essay at my home desk, I am surrounded by wooden shelves that contain perhaps a thousand books. The iPad sitting beside me contains at least three times that number in my digital library. But whereas I can reach any of the physical books in my study in less than five seconds, and can generally get to the parts of them that loom largest in my mental library in well under a minute, it can take that long even to locate a single e-book on my iPad, let alone to find a particular passage. Powerful though the iPad may be—and it is the best e-book reader I know—its heavy dependence on search and scroll still makes it a poor replacement for the library Walter Benjamin unpacked from his crates or the one that surrounds me now.

I had intended to write in this essay about the technical challenges that desperately need resolving if scholars are to migrate toward digital libraries without sacrificing what has been most precious about the memory palaces in which we still store our richest and subtlest understandings of the past. I was going to complain about the breathtaking sloppiness with which Amazon maintains bibliographic control of its e-books, so comically awful that one never knows whether a book will sort by its author's first or last name. I was going to narrate the story of my 20-year effort to build digital libraries on handheld devices, and how frequently I've had to reformat public-domain e-books from .txt to .lit to .html to .doc to .pdf to .mobi to .epub, with no hope of retaining my own annotations in the process. I was going to describe how many times I've had to purchase additional versions of the same beloved book in order to access it on a new device. But I must save that conversation for a longer draft of this essay that will ultimately appear—where else?—in a book where I can give the argument the space it deserves.

For now I will simply repeat what I said at the end of my October column. Those of us who love books inevitably gather a library around ourselves that embodies not just our knowledge but our selves. From this metaphorical library emerge the ever more deeply informed intuitions that enable us to filter the chaos of mere "search results" by exercising human judgment to yield genuine insights and even wisdom. This lifelong process of creating a scholarly self by means of an intellectual and emotional journey whose way-stations are marked by passionately remembered texts—many of them so dear that we keep them close to us for our entire lives—is being transformed in the fragmented world of search and scroll that has become our dominant metaphor for knowledge itself. There is no escaping this transformation. But if we are to preserve the virtues of the scholarly life while enjoying the fruits of these new riches, we must join Walter Benjamin in unpacking the old physical crates that once held our books so we can continue to recollect them in the well-stocked libraries of our minds.

William Cronon (Univ. of Wisconsin–Madison) is the president of the AHA.