The Florentine Codex is an encyclopedic accounting of life in 16th-century Mexico and an invaluable resource for understanding the exchange between European and Indigenous cultures during the Spanish conquest. Emerging from a time of societal upheaval, the codex was written as an attempt to record the culture and beliefs of the Aztec peoples of Mexico in the areas surrounding the once great city of Tenochtitlan. The work covers a broad array of topics, including religion, everyday life, native flora and fauna, and Indigenous perspectives on the conquest itself.

Written at a time when Spanish authorities had been and still were actively undermining Aztec culture and beliefs, the Florentine Codex represents an attempt to document and preserve a past and people being systematically censored. It is the product of many minds in collaboration, written in two different languages by numerous scribes and illuminated by a number of artists employing a uniquely syncretic style of illustration, all of which comes together to create a multifaceted depiction of the culture, language, and history of Aztec civilization immediately following the fall of the empire.

The Florentine Codex was completed sometime between the fall of 1575 and the spring of 1577 after nearly 30 years in the making. Composed of 12 illuminated books with a total of 2,446 pages and 2,472 illustrations, it is widely attributed to a Franciscan friar known as Fray Bernardino de Sahagún (1499 to 1590). Though the modern title of the codex comes from the Biblioteca Medicea Laurenziana in Florence, where it is housed today, scholars do not know what the original title was at the time of its completion. Sahagún himself referred to the text variously in his native Spanish as doze libros ( "twelve books"), obra ("work"), and, perhaps most expansively, Historia general de las cosas de la Nueva España ("General History of the Things of New Spain"). While the codex certainly contains history, its scope is greater than even that title might suggest.

The contents of the Florentine Codex are summarized below:

The folios of this impressive work include text in two languages: Spanish, the language of the intended audience of the codex, and Nahuatl, the language of the Indigenous peoples of Mexico. While the text is bilingual, neither language represents a translation of the other. Instead, the texts exist in parallel, the Spanish frequently interpreting, abbreviating, adding to, or omitting information from the content of the Indigenous language. For this reason, modern scholars have stressed the need to read the two texts in conjunction rather than one on behalf of the other: Though the entries can be read side by side, their meanings are not always in harmony. There is an ebb and flow in the presence of the Spanish and Nahuatl texts; sometimes there is less written in one language than the other, sometimes one is absent from a folio altogether, and even when they are both present, readers might find inconsistencies in their tone, meaning, or content.

Alongside the two languages, the Florentine Codex is punctuated with illustrations. The images in the codex include both decorations and compositions; many are painted in vivid color, while others are rendered only in ink outline, but all of them were illustrated by native artists over the course of years. In the 16th century, images were efficient and impactful ways of conveying information across linguistic and ideological barriers and became a common means of communicating messages in the early colonial world. Painted cloths, wall art, prints, banners, and other means of pictorial expression became tools for religious, political, and social communication, especially in the early days when only a few individuals could translate between Nahuatl and Spanish, much less the other languages spoken in Mesoamerica at the time. The images in the Florentine Codex represent an entirely separate mode of communication, and one with which both cultures would have been intimately familiar, though in different ways.

In the Nahuatl language, Indigenous painter-writers were known as tlacuiloque (singular tlacuilo), and were heirs to an artistic tradition that stretched back centuries before the European colonization of the Americas. Created by such skilled artisans, the images in the Florentine Codex are stylistic adaptations, integrating artistic elements from native traditions with the format and conventions of the European traditional styles, particularly the convention that favored formal isolation of subjects within the layout of the page. While the presentation of the images is generally more European in style, there are several examples of Aztec artistic conventions in the Florentine Codex. These include the use of curling symbols called "speech scrolls" to indicate a speaking individual in a static image, and the practice of depicting seashells on the edges of tendrils of water. Both of these stylistic elements appear in the image of Chalchiuhtlicue from the Codex Borbonicus, which was created by Aztec priests and preserves many pre-Hispanic modes of pictorial representation.

While the texts address audiences in the languages of two cultures, the images of the Florentine Codex represent the clearest examples of the cultural syncretism at play in 16th-century Mexico:

Such a work could have been produced only in Mesoamerica, where the introduction of the Roman alphabet and European art style made sense to people who had been writing and painting with ink and natural colors for centuries. It is among the rare first manuscripts to represent indigenous cultures that involved indigenous people.

(Peterson & Terraciano, 13)

While Fray Bernardino de Sahagún is considered the author of the Florentine Codex, it was actually a product of a substantial collaborative effort and featured the contributions of people from Mexico's Indigenous communities as its primary content. That being said, the codex would have been impossible without Sahagún, whose role included writing, coordinating, editing, and translating, in addition to proposing the actual idea of and advocating for the project itself. Considering the extensive subject matter and sheer volume of scribal and artistic labor involved, one man, even one as ambitious as Sahagún, could not have accomplished the ambition of this project alone.

Sahagún was a teacher and missionary absolutely dedicated to the conversion of the native people of Mexico to Catholic Christianity. He believed that in order to accomplish his goal, he had to understand the belief systems, culture, and language that had preceded the colonial influence of Spain. After all, missionaries could not ideologically eclipse a religion they could not recognize and could not convey Christianity without sharing a common language with their prospective converts. But Sahagún and his peers in the church had come to Mexico after the conquest and had little to no knowledge of Aztec civilization. In order to accomplish his ultimate evangelical aim, Sahagún had to rely on information from those he sought to convert.

Beyond just content, Sahagún needed help with the recording process. The nearly 2,500-page Florentine Codex was drafted multiple times over the course of three decades through the concerted efforts of a number of steady-handed and literate men. These men were intellectuals, born in Mexico to Indigenous parents and then educated at colleges sponsored and staffed by the Spanish church. They, like Sahagún himself, were fluent in Nahuatl, Spanish, and Latin, and were instrumental in the creation of the codex, a process that occurred largely in the later years of Sahagún's life, when age rendered the friar incapable of writing anything himself with his own trembling hands. Though he was certainly the author of the prologues and parts of the Spanish text, those sections represent less than half of the content of the Florentine Codex.

From 1559 to 1565, Sahagún and his collaborators collected what would become the Florentine Codex in conversation with elders in the settlements of Tepepulco and Tlatelolco. During his time in Tepepulco, Sahagún worked with local authorities to assemble a group of approximately twelve elders. These elders had all lived through the cataclysmic arrival of Hernán Cortés and his forces and could offer their knowledge of the pre-Hispanic Aztec culture to Sahagún's project. After the friar and his team of scribal scholars recorded their spoken testimony, the elders offered images representing what they had said. As mentioned above, Aztec tlacuiloque had kept history and culture in pictorial records long before the advent of the Roman alphabet in Mexico.

After three years in Tepepulco, Sahagún and his nascent codex were transferred to Tlatelolco, where he once again presented his intentions and requested leaders from among the native peoples. With about ten more elders, all of whom were capable and knowledgeable in Nahuatl and the preconquest customs of the Aztecs, Sahagún and his team proceeded to expand on, clarify, and revise the work.

When the friar concluded his interviews in Tlatelolco around 1565, his collaboration had produced what is known today as the Códices Matritenses or Madrid Codices, an early draft of the Florentine Codex. Like its later iteration, the Madrid Codices are written in Spanish and Nahuatl, but unlike the Florentine Codex, the 1565 draft is not illustrated and includes three columns of text. The left columns, written in Spanish, encompass Sahagún's notes on the same subjects addressed in the central columns, all of which were written in Nahuatl on specific topics. The columns furthest to the right, which do not appear in the Florentine Codex, articulated Sahagún's lexical notes on the Nahuatl language. The friar had planned to include the third column in the Florentine Codex as well, but a lack of time and support, in Sahagún's own estimation, prevented his culminating work from being the linguistic resource he had intended it to be.

At this point, Sahagún describes editing, dividing the content into twelve books and sorting the text into specific chapters and paragraphs. He writes:

The Mexicans corrected and added many things to the twelve books as they were being copied anew, in such a way that the first sieve through which my works were strained was that of Tepepulco; the second, that of Tlatelolco; the third, that of Mexico.

(Book 2, folios 1v-2r, translated by García Garagarza)

Among the hands and minds that sieved his works, the friar mentions a few by name. Though it does not represent a complete list of his Indigenous collaborators, Sahagún mentions Martín Jacobita, who was director of the colegio of Tlatelolco, Antonio Valeriano, who was a native of Azcapotzalco, and two natives of Cuauhtitlan named Alonso Vegerano and Pedro de San Buenaventura, all of whom were experts in Latin, Spanish, and Nahuatl. In his list of scribes, he includes Diego de Grado and Bonifacio Maximiliano, both natives of Tlatelolco, and Mateo Severino from Xochimilco. Peterson and Terraciano assert that there were many other unnamed collaborators from the communities surrounding Lake Texcoco that contributed to the final product. Sahagún ultimately delivered a book containing far more than was necessary to convert the native population to Christianity. He created a vehicle through which Nahuatl authors and artists of the 16th century can still be heard and seen today.

In his prologue to Book 1, Sahagún articulates multiple aims for the practical use of the Florentine Codex. The first of his goals naturally centers on his role in converting the native population. Likening the work of missionaries to physicians tasked with diagnosing and treating illnesses, he claims that as physicians care for the body, priests and confessors are meant to minister to the souls of those whom they aim to convert to Christianity. In order to accomplish that task, he asserts that it was necessary to record accurate accounts of the language and beliefs of the Indigenous peoples of Mexico before the Spanish conquest. These linguistic and anthropological endeavors become the other stated goals of the codex.

The presence of so much Nahuatl language in the codex represents the scope of Sahagún's dedication to this goal. By 1540, well before initiating the project that would become the Florentine Codex, he had already authored a number of sermons in Nahuatl, enough to be delivered at all of the saints' days and Sundays of the year. He had tailored these to the Indigenous people, both the nobility and the lower classes, not just in their language but according to the aptitude he recognized in them at the time. As he learned more, the friar would find that their capacity not only exceeded his expectations but evoked in him a profound respect for their way of life, which would inform and enhance his convictions in his anthropological aim.

While it is not clear exactly when this sentiment formed for Sahagún, he makes it clear that one of his goals is to demonstrate the worth of the peoples who had suffered devastation at the hands of Cortés and his forces. Early in the Florentine Codex, Sahagún quotes an Old Testament prophecy attributed to Jeremiah, asserting the similarities between the prophetic portents and the fate of the Indigenous peoples in the conquest of Mexico:

"I will bring a people upon you from far: it is a mighty people and courageous, it is an ancient people, and skillful in fighting, a people whose language you will not understand, nor have you ever heard their manner of speech—all of them mighty men and courageous and with a great lust to kill. This people shall destroy you, and your women and children, and everything that you possess; and they shall destroy all your towns and buildings." This, to the letter, has happened to these Indians at the hands of the Spaniards. They were so utterly trampled upon and destroyed, with all of their things, that no resemblance was left of what they were before.

(Book 1, folio vir, translated by Garagarza)

Sahagún further laments that the native peoples are perceived as barbarians despite the fact that their styles of governing, as he puts it, are "far ahead of many other nations that presume to be highly civilized" (Book 1, folio vir, translated by Garagarza).

Sahagún continues his praise of the Indigenous people—particularly their educational systems, rhetoric, and achievements in arts, sciences, and technologies—throughout the rest of the Florentine Codex and even compares the cultures of Mesoamerica to Troy, Rome, Carthage, and Venice, emphasizing their similarities to those highly esteemed civilizations of Europe. While he qualifies all of this praise with a notion of Mesoamerica being a place apart from the influence of God, where the devil has enjoyed prosperity, he nonetheless situates the native peoples of the Americas as kin to the Spanish and as mutual descendants of Adam.

In writing to his Spanish audience, whose perspectives likely would have been influenced by biased accounts from the conquistadors, Sahagún went far to assert the worth of the culture and heritage of Mexico's Indigenous population. In some ways, he went much further than would have been comfortable to his fellow Spaniards:

For Spanish officials, particularly ecclesiastical authorities, words in native tongues were inherently suspect and images potentially idolatrous; translation itself might camouflage heretical ideas and harbor dangerous political meanings.

(Peterson & Terraciano, 14)

Almost certainly aware of this idolatrous potential, Sahagún still championed a text largely written in Mexico's native tongue and richly illustrated by Indigenous artists. Even when King Phillip II of Spain (reign 1556 to 1598) ordered the confiscation of all manuscripts involving Indigenous history and religion in 1577, Sahagún may have withheld a copy of his codex, in defiance of the Crown, and offered to copy and send it again to be sure it was received. The codex was sent to Europe in the year of the decree, was acquired by the Medici family in 1587, and disappeared from the historical record for nearly two centuries. The codex was rediscovered in 1793, but was not actually studied until 1879, and was inscribed in UNESCO's Memory of the World Register in 2015.