When lecturing undergraduates on ­Kafka’s Metamorphosis—during his otherwise idyllic American years, when he had to make his principal living in the classroom—Vladimir Nabokov liked to call his students’ attention to those sparse textual clues that made it possible to deduce what kind of “monstrous vermin” it was that Gregor Samsa had changed into during the night. Precisely why Nabokov did this might not have been immediately obvious to his charges. Perhaps it was only a brief, pardonable moment of ostentation, like casually drawing an exquisite watch from one’s waistcoat pocket not because one really has any need to check the time but only to dangle it for a glittering instant before the eyes of the hired help. It certainly allowed him to flaunt his considerable entomological expertise before a captive audience. It even allowed him to demonstrate that he understood aspects of the story better than its author ever had. (Kafka might have been able to describe the insect in question, but it is doubtful he could have named it.)

In fact, however, Nabokov’s motives were largely both pure and high. For him, there was no such thing as a ­merely incidental feature in any text—at least not in any text truly worthy of notice. He regarded it as of the very essence of reading that one know as exactly as possible what one is reading about at any instant. He approached every text in this way. He would lavish loving, sometimes obsessive scrutiny on every concrete detail of the story: trees and butterflies, the designs of drawing rooms and gardens; whatever flora might be springing up in the margins of the page, whatever unguiculate or sleekly squamous fauna might be slinking between its lines or scurrying from one paragraph to the next; the angles of shadows, the songs of birds; and so on. For him the special delight of literature, and in fact its special coherence, lay always in the particular: in the discrete details the author had gathered up into his prose and in the texture produced by their interweaving. And no one was more brilliant at noticing those details. Nabokov was an absolute master of—in the parlance of earlier ages—literal exegesis.

That, though, is not how we would tend to think of it today.

Historians or hermeneuticians frequently assert that what most alienates modern readers from the methods of premodern exegetes is the latter’s passion for allegory. But this is false. If anything, we today are much more culturally predisposed than our forebears to an unremitting allegorization of the tales we tell or books we read, no matter how elaborate or tedious the results. True, we may prefer to discover psychological or social or ­political or sexual narratives “encoded” in the texts before us, rather than spiritual or metaphysical mysteries; we might find it impossible to believe that a particular reading could be “inspired” in a more than metaphorical sense; but the principle of the metabolism of the fictions we read into the “meanings” we can produce is perfectly familiar to us. The same critic who might prissily recoil at the extravagances of a patristic figural reading of the Book of Numbers might feel not the slightest dismay at the transformation of Prospero into an ironic indictment of ­colonialism, or of Horatio Hornblower into an inflexibly erect emblem of the “phallic signifier.” What makes the spiritual allegories of ancient pagan, Jewish, and Christian exegetes so alarming to modern sensibilities is not that they were allegories but that they were so disconcertingly spiritual.

Where our understanding of what a text is and of how to read it differs most radically from that of our benighted ancestors—those poor slouching brutes who invented philosophy, the plastic arts, the hospital, Doric columns, flying buttresses, stained glass, and all the rest of that savage gallimaufry of gauds and baubles—is in our notion of what a “literal” interpretation is. All the term means to us today is a literalist construal of a text: that is, taking a text as an accurate documentary account of real events. Thus to read Kafka’s Metamorphosis literally would, for us, mean earnestly believing that at some precise moment in the past Mr. Gregor Samsa really did awake in his bed in Prague to find himself transformed into an enormous beetle.

For ancient and medieval exegetes, however, the very question of whether the events recounted in the text had ever actually happened was largely a matter of indifference for how to go about reading the text literally—or, more precisely, reading it ad litteram: that is, with an exactingly scrupulous attention to what was written on the page, in every detail, and with every discernible shade of significance. For them the difference between the literal and the allegorical was simply the difference between what was there to be seen and what was given to be discovered. And their somewhat insouciant attitude to the question of “fact” can prove terribly confusing to modern readers who do not share their presuppositions.

This is especially true in the case of Christian theology. After all, no one today is likely to imagine that Porphyry believed Homer’s Cave of the Nymphs episode to be a true story, in the most reductive sense; surely, though, it should not be impossible to determine what a premodern theologian believed about the historical veracity of the scriptural episodes he commented upon. But really the question rarely arose. Sometimes we can tell. It seems clear that Gregory of Nyssa did not believe that God ever truly slew the firstborn of Egypt, but that Augustine did believe that God sent two bears to mutilate the children who mocked Elisha. Augustine accorded the story of the Garden of Eden a degree of historical substantiality that Origen explicitly denied it. There was room for variance of opinion, dependent on temperament, theology, credulity, and moral imagination. But, whatever the case, the historical issue was quite irrelevant to how “literal” any given reading of Scripture was. The documentary value of Scripture was so secondary a matter that often we can only guess what the exegete’s “historical” view of any given story was. When Origen pondered the physical dimensions of Noah’s ark, was it because he believed the story to be “literally” true in our sense? Who can know? What we do know is that by paying such close attention to the details of the story he was establishing a basis upon which other, more spiritual readings could be stably raised.

Hence Thomas Aquinas’s assertion that, among the various senses the exegete finds in Scripture, the primary and most indispensable is the literal. He was not proposing that one should assume the historical veridicality of everything one reads in its pages, but only that one must carefully ascertain what the text actually says before one ventures to say what more may be found there. It is an admonition against constructing some other text that better conforms to the interpretations one wants to produce. The meaning must arise from the actual images and words provided; a rose is a rose is a rose; it is not a lily. Not only is Thomas’s principle not an exhortation to modern fundamentalism, it does not even entail a reading of Scripture that we today would necessarily recognize as literal at all. The most effulgently beautiful work of patristic literal exegesis is ­Augustine’s De Genesi ad litteram (On the literal reading of Genesis); but scarcely any modern reader could distinguish much of it from an exercise in allegory; at times, what Augustine presents as the plain meaning of the text reads like a rapturous and brilliant discourse on its metaphors.

Anyway, no need to belabor the point. Suffice it to say that we today approach the texts we read with expectations and under categories so different from those of our more distant predecessors that it may not be an exaggeration to say that the books we share with them in common (like the Bible) are not really the same books at all. We cannot inhabit texts as they did, and they would certainly find our ways of reading strange and inhos­pitable. For them, the various senses of the text were separated by subtly shifting degrees of intelligibility and imaginative resonance and significance, both implicit and explicit; for us, the act of reading often devolves into a stark alternative between, on the one hand, the symbolic or fanciful and, on the other, the documentary or “literal.”

In either case, interpretation is rendered more impoverished than it might have been, precisely on account of this absolute and unambiguous distinction. Inevitably, so pronounced an antithesis forces its poles toward ever more irreconcilable extremes. We feel we must choose, or at least spasmodically lurch, between the “literal,” which is merely aridly factual, and the “symbolic,” which is merely vapidly illustrative or didactic or edifying or hortatory (or whatever). Occasionally, a reader of genius like Nabokov might be able, instinctively, to fly free from so confining a set of alternatives, but that is an aberration. And the pity of it all—no matter what our critical or theological principles may require of us—is that most of us will never be able to experience, as some of our ancestors could, just how rich, variegated, absorbing, ingenious, and inspired the act of reading can be.