Sermon 33 from the 1427 Sienese circle of sermons by Bernardino da Siena, reveals the important role Dante and the Comedy played as a source of vernacular lay scientific and theological knowledge. [1] In it, Bernardino describes Lucifer’s fall and his confinement to the center of the Earth:

[...] dove cadde costui [Lucifero]? ‘in terram.’[...]la terra è fredda. Se in nessuno luogo stanno i giacci, si stanno in terra[…] per la freddezza della terra[…] dico, che la terra è grave, che sempre va in giù. Piglia la pietra, e lassala andare: non si resta che ella ha toccato il fondo; e se fusse possible che ne la terra si facesse una apertura che passasse insino di sotto, dove si potesse vedere l’aria, gittandovi uno sasso o pietra si fermarebbe nel mezzo, cioè nel centro de la terra.
E Lucifero fu fatto cadere del cielo in terra: dove aveva prima quelle condizioni chiare e splendide e leggiere, subito cascato prese le condizioni de la terra; cioè che il volere suo diventò freddo al far bene, el potere diventò grave e ponderoso, el sapere diventò oscuro e tenebroso. E perchè queste condizioni so’ poste nel centro de la terra, peró è posto il suo luogo nel centro de la terra, e non più là né più qua. [2]

When Lucifer’s physiognomy changed in the act of sin, and he became heavy, dark and cold, his body, in line with Aristotelian physics, was attracted to its “natural place” and thus drawn to the center of the Earth, whose traits are darkness, coldness and heaviness. In order to explain how all heavy matter in the universe is drawn to a single point in the center of the Earth, Bernardino describes a thought experiment in which a stone is dropped into a hypothetical hole, dug all the way to the other side of the globe. Using this experiment, Bernardino leaves his audience to surmise that the continuation of such a fall would mean a contradiction of both natural law and common sense, as the stone would be “falling upwards” relative to the people on the other side of the globe.

Although presented as self-explanatory, this thought experiment would not have been so easily understood as a valid description of Lucifer’s fall by any mixed lay audience unfamiliar with the Comedy. [3] Bernardino’s narrative owes much to Dante’s conception of Lucifer’s fall, and outside of the Dantean context, some of Bernardino’s ideas, such as Lucifer being encapsulated in ice, or even the world as round with God at its circumference, would have seemed strange to the uneducated city dweller in the audience. More important, without the context of Dante, the thought experiment would not really answer the problem of Lucifer’s fall. If one is to refer only to Bernardino’s experiment, should not Lucifer have collided with the Earth’s crust rather than gone through to its center? It is only the description of the Earth’s retreat before Lucifer in Inf. 34.121-126, with which the audience is familiar, that makes this experiment seem possible. It is also the Dantean context of Virgil’s speech in Inf. 34 that resolves the apparent contradiction of this sermon’s narrative with that of another of Bernardino’s Sienese sermons, which states that the Earth could not suffer Lucifer’s weight. [4]

Bernardino’s sermon is remarkable, however, not only in its demonstrating that Bernardino borrowed from Dante ideas rather than just literary motifs, or in its use of the audience’s familiarity with a vernacular secular literary work, but also in its direct indebtedness to 14th-century vernacular Dante commentaries.

It appears that the source for both the language and the ideas in Bernardino’s description can be traced to popular commentaries on the Comedy that preceded Bernardino’s career by a century. Thus, L’Ottimo, and other commentaries after it, describes exactly the same thought experiment in the context of explaining Lucifer’s location at the center of the Earth: [5]

S’elli fosse possibile di trovare, o di fare uno foro in questa terra del nostro emisperio che noi abitiamo, e fosse di tanta profondità, che toccasse l’altra ultima parte della terra[…] e per questo foro dall’altra parte del nostro emisperio si gittasse un sasso di sotto verso l’altro emisperio; conciosiacosachè ’l sasso sia corpo grave, e proprio è della natura del corpo grave di discendere; imperò questa pietra discenderebbe infino a questo punto, che noi chiamiamo centro, rimotissimo sopra tutti gli altri, e igualmente distante dal cielo: e quando questa pietra fosse in questo punto, sì dimorrebbe in quello sanza muoversi per necessaria ragione di natura[…] E così si conchiude, che questo centro è intra l’altre parti dello Inferno la più orribile e più profonda, perciò ch’è più remota dal cielo, e da Dio, primo principio. E però in questo profondo, sì come in convenente seggia, e co[n] sì acerbo giudicio di Dio è tormentato, e dimora l’angelo tenebroso Lucifer; però che levato contra il suo Fattore per mattezza di superbia, volle apparere simile a lui; del quale scrive Isaia dicendo: come cadesti del cielo, o Lucifero, che la ‘ndomane risplendevi, e ti levavi?

The similarity between Bernardino’s text and L’Ottimo’s speaks for itself. A century before Bernardino’s sermon, L’Ottimo describes the same experiment (digging a pit and throwing a stone in it) in order to explain the same idea (pre-Newtonian center of gravity) in exactly the same theological context (an explanation of Lucifer’s fall). L’Ottimo’s description is much more detailed, giving a geometrical explanation on why a stone would stop as the earth’s center (the center of the circle being the furthest point from the circumference), thus adding another facet to the symbolism of the center of the Earth as the farthest place from God.

L’Ottimo’s treatment of this subject was well known and copied by other commentaries, such as that of the Anonimo Fiorentino. It should be noted that although thought experiments similar to the one cited here were made by such scholars as Albert of Saxony (c.1320-1390) and Nicolas d'Oresme (c.1323-1382), it appears that these experiments were not made in relation to Lucifer’s fall, but were used to prove precisely the opposite point, namely that a stone would not stop at the center but oscillate about it because of its momentum. [6]

It appears that even Bernardino’s various descriptions of the earth’s traits and location as befitting Lucifer’s sin [7] may have been influenced by Jacopo della Lana’s commentary paralleling the traits of Heaven and Lucifer’s seraphic state with the traits of the Earth and Lucifer’s postlapsarian state. [8]

While Jacopo della Lana uses the terms “grandi, lucidi e chiari” to describe the heavens, Bernardino uses “chiare e splendide e leggiere.” And while Bernardino, who is famous for his elaborations of and fondness for neat scholastic categorizations, may use these ideas differently from Jacopo della Lana, who favors a less rigid structure, Bernardino still clearly utilizes variations of Jacopo della Lana’s ideas and language.

Bernardino’s dependency on Dante is of great importance. When Bernardino employs a unique description of Dante’s to depict a theological truth (the angelic fall, for example), he avails himself of a readymade literary image from the audience’s popular culture (a literary image that is supposed to be fictitious) and upgrades it to a new status, de facto making it a valid description of theological truth.

When Bernardino takes, modifies, and uses the commentary tradition on Dante’s description, he is demonstrating one of the ways in which mendicant preachers used popular vernacular texts. Texts such as these, produced by the lay intelligentsia operating in this urban culture, were evidently used not only as exempla, but also as valid sources of scientific explication, handy sources in the vernacular ready to be utilized for the edification and enticement of the diverse crowd of lay sermon-goers gathered in the Campo di Siena.

[2] Siena 1427 33.19-22: Bernardino da Siena, Prediche Volgari sul Campo di Siena 1427, ed. Carlo Delcorno (Rusconi, 1989), 940, et al.

[3] It is evident from other sermons that the Sienese audience was well versed in the Comedy; thus Bernardino simply says “sai come disse colui” before quoting the Comedy, knowing the audience would recognize the quotation even without the name of the author. See Siena 1427, 23, Bernardino-Delcorno, Prediche Volgari, 676.

[4] Siena 1427 13.10: Bernardino-Delcorno, Prediche Volgari, 391: “per la gravezza tua non ti poté sostenere né ’l cielo né la terra.”.

[5] L’Ottimo, Inf. 34.68-69; Bambaglioli, Inf. 34.68-69; Anonimo Selmiano, Inf. 34.76-81; Anonimo Fiorentino, Inf. 34.78-80 etc.

[6] See Edward Grant, Planets, Stars, and Orbs: The Medieval Cosmos, 1200-1687 (Cambridge University Press, 1994), 660-661, note 137.

[7] Siena 1427 33.119-120: Bernardino-Delcorno, Prediche Volgari, 961; Siena 1427 33.19-22: Bernardino-Delcorno, Prediche Volgari, 940; PS 1427 13.10: Bernardino-Delcorno, Prediche Volgari, 391.

[8] Lana, Inf. 32. Nota.