In an intriguing passage from Thomas Harris’s psychological thriller Hannibal (1999), the reader is introduced to a mental technique used by the eponymous serial killer, Dr. Hannibal Lecter:

The memory palace was a mnemonic system well known to ancient scholars who preserved much information in them through the Dark Ages. Like the scholars before him, Dr. Lecter stores an enormous amount of information keyed to the objects in his thousand mental rooms . . . .

Hannibal’s palace is vast, even by medieval standards. Translated to the tangible world it would rival the Topkapi Palace in Istanbul for size and complexity.

As Harris suggests, such labyrinthine and intangible “mind palaces” do not solely belong to the pages of fiction; they are in fact one of history’s most unusual, and important, footnotes. Although it has a whiff of the apocryphal, the method of loci—or the memory-palace technique, as it has become more colloquially known—in fact had a powerful impact on the development of the Western intellectual tradition. Today, however, the idea that a palace, cathedral, or some other imaginary work of architecture can be constructed in the mind, and whose individual rooms can be populated with memories, has been abandoned as a dust-shrouded relic of the past.

The roots of the technique reach back to antiquity and the Greco-Roman world. The method of loci, as it was then called, was concerned with the amelioration of memory. It yielded breathtaking results by allowing users to store a vast cache of information in their minds and to retrieve this data almost instantaneously. The technique was put to use by Roman senators, Dark Age Christians, and Renaissance thinkers.

And yet, for all the subsequent scholarship we have on the technique, no one is certain precisely from whom, or even where, it originated. As is often the case in such situations, a forgotten beginning, veiled by the passage of time, was replaced with something more palpable—an invented legend or fable that acted as an antidote to the unknowable. Thus we find the mythological genesis of ars memoriae, the art of memory, in a story recounted by Cicero in his De Oratore.

No one is certain precisely from whom, or even where, it originated.

At some point in the fifth century B.C., the tale goes, Poseidon—the god of the sea, storms, and earthquakes—emitted a malevolent tremor that leveled an assembly hall in Thessaly. The structure came down upon the heads of a party of banqueters who had gathered in honor of a nobleman named Scopas. Death was inescapable for all but one of the men. A fortuitous moment earlier, the Greek poet Simonides of Ceos had been summoned away from the feast, and the building’s impending collapse, by two messengers. He returned in astonishment to find the ruined hall and the unrecognizable bodies of the revelers, mutilated and entombed as they were by the fallen stonework. No one could tell who was who in the wreckage; chaos and confusion prevailed.

And then something extraordinary happened. Standing in front of the razed building, Simonides closed his eyes, withdrew into his imagination, and reversed time in his mind. The ruined marble pillars reassembled themselves into their cylindrical wholes and the shattered pieces of frieze levitated back into the air above the long banquet table. The noble Scopas and his friends came back to life in all their ill-fated revelry, laughing and talking to each other heedlessly. Simonides, somewhat miraculously, found that he could remember exactly who all the banqueters were as he visualized them sitting around the table in the great hall. Resurfacing from his meditations, he was immediately able to identify each mangled corpse.

It was at this moment, according to the legend, that Simonides discovered the fundamental principles behind the art of memory. He noted that he had been able to remember where each guest was sitting because of his effortless recollection of the banqueting hall’s space (the layout of which he had not deliberately studied) and, more importantly, the positions of the guests within that space. He realized that the key to faultless remembrance lies in the organization of memories. They could be organized and placed, as individual entities, in an imagined architectural space—analogous to the way the Thessalonians were distributed around the great hall.

This approach structures and stores information in a systematic way, much like a cerebral filing cabinet.

This approach structures and stores information in a systematic way, much like a cerebral filing cabinet. Whereas unorganized memories float freely around the brain, as it were, and are susceptible to being forgotten, the memory that is affixed to an appointed location will be, if maintained correctly, unforgettable. But how are these memories to be manifested? How exactly does one “store” a memory in an intangible building? In the second part of the memorization process, the practitioner associates the thoughts and ideas to be remembered with vivid images. These visual markers are then strategically deposited around the imagined spatial environment at certain fixed points. One then simply has to “walk” back through the corridors of the mind and retrieve the ideas residing in a palace’s various rooms. This step is crucial: without the creation of these evocative images, the palace would be an empty, sterile, and ultimately useless space, comparable to a museum or gallery with barren walls and unadorned plinths.

Could Simonides not, he reckoned, use the hall and the positions around the table as depository places for a chronological lineage of Greek philosophers? Or the words to one of his poems? Or the tasks he needed to complete that day? The possibilities were endless. Just about anything that could be imagined, he reasoned, could be permanently implanted in one’s mind simply by leveraging one’s innately exquisite spatial memory. Everything here revolves around our inherent ability, as humans, to be keenly aware of our surroundings. An explanation for this can be found in evolutionary biology: eons of natural selection have conditioned the human brain to be hyper-sensitive to spatiality. This was a trait of existential importance to our early ancestors: hunter-gathers needed to be in no doubt as to the location of fertile hunting grounds, where dangerous predators were likely to roam, how to return to campsites, and so on. What Simonides essentially discovered was that our heightened locational awareness can be used advantageously in memorization.

The story of Simonides and the banqueting hall is, of course, in all likelihood a fabricated parable. We know that Simonides existed, but we cannot be sure that he was the source of these revelations. And yet the fact remains that some ancient thinker, or confederation of thinkers, inadvertently stumbled upon a mnemonic technique whose efficacy shaped the intellectual climate of the centuries that followed. Although it seems improbable now, the method of loci was widely practiced in classical antiquity, becoming a cornerstone of the Western pedagogical tradition.

The intellectual giants of their day all possessed immaculate recall

After wide practice in ancient Greece, the system was inherited and further refined by the Latin world. Romans like Cicero and Quintilian codified its rudiments into a set of rules, contained in instruction manuals, that guided aspiring practitioners. It was taught as part of a civilized Roman’s curriculum, conceived as a sort of useful cognitive technology—not to be learned for its own sake, but rather to complement other disciplines. Would-be orators deployed the technique as a cognitive aid for memorizing speeches. Indeed most of our extant evidence for the method is embedded within treatises concerned with rhetoric, a subject that constituted one third of the Trivium, along with grammar and logic. (The Trivium was itself a centerpiece of classical education, as the lower division of the seven liberal arts. This program of learning later proved instrumental in the birth of the modern university—as at Bologna, Paris, Oxford and Cambridge, Padua, Salamanca, and Coimbra.) In the Rhetorica ad Herennium, an anonymous first-century-B.C. pamphlet and one of the oldest surviving Latin texts on memory, it is made clear that memorization techniques were an integral part of the Roman orator’s intellectual armory. They endowed him with an accurate and nimble recall that facilitated elegant, and seemingly effortless, speech—invaluable, for example, to the time-pressed senator who had to deliver frequent addresses in front of the senate.

In an ancient world where a heavy premium was placed on parchment, memory was considered an indispensable tool (the thinkers of the deep past were not afforded the luxury of the printing press). The intellectual giants of their day all possessed immaculate recall—a fact that is continuously reiterated by the innumerable anecdotes on supernormal memory in our source material. In Pliny the Elder’s Naturalis Historia, for instance, we are told that King Cyrus, the founder of the Achaemenid Empire, could remember the name of every single soldier in his sprawling army. Pliny goes on to tell us that the Skeptic philosopher Charmadas could recite “the contents of any volume in libraries that anyone asked him to quote, just as if he were reading them.” Seneca the Elder reputedly had such a phenomenal memory that he could parrot back two thousand names in the order that they’d just been given to him. Augustine of Hippo, in De Natura et Origine Animae, marvels at the ability of his school friend Simplicus who, we are admiringly informed, could recite Virgil word-for-word backwards.

Augustine, in The Confessions, speaks of the technique almost as a kind of mental sanctuary.

Thanks to the influence of Augustine and other early Christians, the method did not then disappear, like so much else, with the disintegration of the Roman Empire, but instead flourished in the monasteries of the Middle Ages. After the Visigoths and Vandals sacked Rome, scholars and monks employed the technique to commit entire religious texts to memory and as a means of preserving their most important teachings in a hostile and barbarized world. It is interesting to note that Augustine, in The Confessions, speaks of the technique almost as a kind of mental sanctuary, or panacea to the ills of reality. Memory, in his words, is a “great field or a spacious palace, a storehouse for countless images of all kinds”; it is an “inner chamber, vast and unbounded,” into which images are “seized with marvelous speed and are put away as if into wondrous cells.” This reiterates the two fundamental premises of the mnemo-technic tradition, as we have previously seen—memory ex locis et imaginibus, or “from places and images.”

Harbored in the ark of Christian thought, the method of loci had, at this point, been transformed from a tool of rhetoric into an instrument of pious meditation, and was conceptualized as such by medieval scholastic philosophers. In this new context, memory was seen as a key virtue—necessary not just to regurgitate important points of doctrine, or the finer nuances of a sermon, but also as a means to internalize information of a sacred nature. Only through memorizing, the logic went, could an idea truly be absorbed into one’s psyche. With this assimilation, the acolyte would gain values and ideals that would strengthen his personal ethics and moral character. It is revealing that one of the universal themes in the lives of saints—apart from their impossible virtue—is their razor-sharp recall. The cavernous memories of these medieval and early Renaissance Christians did not contain inconsequential data or ideas, but meaningful knowledge that served a spiritual function. Memorization to them meant a type of transmutation of the metaphysical into flesh and blood. Petrarch echoes this idea in a letter to a friend: “I have thoroughly absorbed these writings, implanting them not only in my memory but in my marrow.” Foundational texts like the Bible were mnemonically engraved onto a devotee’s heart and soul, a notion that the seventeenth-century Dutch poet Jan Luyken neatly summarized with his observation that “one book, printed in the Heart’s own wax/ is worth a thousand in the stacks.”

Perhaps unsurprisingly, Gutenberg’s invention marked a new, poorer era for mnemonic systems.

By the end of the Renaissance, a millennium after Augustine, the method had become organically tied, more or less as a mystical art, to the occult and esoteric Hermetic traditions. And after that? It all but vanished. The leading part that memory played in intellectual life was dampened by the momentous technological advance of the printing press in fifteenth-century Germany. Perhaps unsurprisingly, Gutenberg’s invention marked a new, poorer era for mnemonic systems. With readily abundant books, advanced memorization techniques became obsolete as the printed page began to perform the arduous tasks of remembrance. Why would scholars squander time memorizing something that could easily be referenced in the growing libraries?

The method of loci’s descent from ancient Greece to Rome, Rome to Christian Europe, and Christian Europe to the Renaissance attests to the fact that it has always been positioned, in the words of the historian Frances Yates, at the “great nerve centres of the European tradition.” After the Renaissance, the technique continued to subsist during the scientific revolution and the subsequent Enlightenment, known and discussed by thinkers such as Francis Bacon, Descartes, and Leibniz. In these crepuscular years, however, its renown did not extend beyond a select group of cognoscenti, and by the dark eve of the modern world, its importance had waned to obscurity.

The technique did experience a minor revival in the second half of the twentieth century as an aid to participants in international memory competitions. Within this odd niche, it is used to recall large numbers of items in order, like a pack of playing cards or the decimal places of pi. Apart from such isolated cases, however, and occasional references in popular culture like Hannibal or the television show Sherlock, the practice appears to have no place in the world today. Indeed, in our attention-deficient age, the method of loci may seem hard to fathom. Why trouble ourselves with rigorous memorization when unlimited information hums at our fingertips? Our modern culture is, after all, reliant on a basilica of externalized memories, with vast reservoirs of information stored outside our minds. So why expend energy on mastering a technique that appears to be hopelessly anachronistic?

The simple answer is that we are beginning to suffer from a collective amnesia that has been brought about by the internet’s omniscience and the resulting torrent of information that floods through our daily lives. In spite of this unprecedented availability of data, we retain but meager drops of meaningful knowledge. In short, we have forgotten how to remember properly. As T. S. Eliot, ever prophetic, observed: “Where is the wisdom we have lost in knowledge?/ Where is the knowledge we have lost in information?”

Insofar as we are the culmination of our experiences, it is axiomatic to state that memory is pivotal to the human condition, our knowledge of the world, and our personal past—it permeates everything we do as people. The method of loci, as part of the intellectual inheritance of the Western tradition, reminds us that the cultivation of this most fundamental of human faculties is something never to be neglected. The ancients, those infallible guides to the human condition, remind us that mastery of one’s memory is mastery of one’s self.