Books by Philipp Nothaft
Leiden: Brill, 2023
This volume makes available two little-known twelfth-century Latin sources on mathematical astron... more This volume makes available two little-known twelfth-century Latin sources on mathematical astronomy: the anonymous Ptolomeus et multi sapientum… (c.1145), which is attributable to the famous Jewish astrologer Abraham Ibn Ezra, and the surviving second part of Robert of Chester’s Liber canonum, which accompanied the Tables of London (c.1150). Both texts are introductory-level works originally written to educate a Latin Christian audience in the concepts and techniques involved in computing with astronomical tables. They are here presented in critical editions with facing English translations. The accompanying introductions and in-depth commentaries elucidate their significance in the context of twelfth-century Latin astronomy.
Leuven: Peeters, 2022
This critical edition of the Cistercian astronomer and conciliarist Hermann Zoest of Münster’s 'D... more This critical edition of the Cistercian astronomer and conciliarist Hermann Zoest of Münster’s 'De fermento et azimo', surviving in a dozen complete manuscripts, makes available the greatest medieval treatise concerning the type of bread that Jesus broke at the Last Supper. Since the so-called Schism of 1054, the Greeks, who employed ordinary leavened bread in the sacrament of the Eucharist, routinely claimed that the Latin use of unleavened bread was invalid and did not involve the Body of Christ. Hermann composed his treatise in 1436 at the Council of Basel, with the oecumenical goal of facilitating Church Union. Relying on astronomy, biblical exegesis, conversation with Greeks, and, in a later revision, information from the famous Jewish convert Bishop Paul of Burgos, Hermann came to the conclusion that the Last Supper occurred before Passover when the Jews were still eating leavened bread, although he allowed for the possibility that Jesus established a new rite with unleavened bread. After enumerating the disagreements between Greeks and Latins, Hermann advised that they focus on the faith and ignore what he labelled ceremonial differences.
A Fourteenth-Century Chronologer and Critic of Astrology: Heinrich Selder's "Treatise on the Time of the Lord's Annunciation, Nativity, and Passion"
Oxford: Oxford University Press, 2022
This volume makes available a newly discovered work by the Swabian astronomer Heinrich Selder (fl... more This volume makes available a newly discovered work by the Swabian astronomer Heinrich Selder (fl.1365-79), a hitherto overlooked figure in fourteenth-century intellectual history. Composed from 1371 to at least 1379, this 'Treatise on the Time of the Lord's Annunciation, Nativity and Passion' (Tractatus de tempore dominice annunciationis, nativitatis et passionis), records Selder's surprising views on two seemingly unrelated questions: the dimensions of history and the folly of astrology. Drawing on a diverse range of sources, from ancient Roman poets to the writings of a twelfth-century mystic nun, his 'Treatise' documents a sophisticated and prescient attempt to reconstruct the chronology of early human history, from the creation of the world to the birth of Christ, in a scientifically sound manner. Woven into these discussions is a fierce attack on the rationality and legitimacy of judicial astrology, which spotlights Selder as one of the most radical critics of this art and its practitioners in fourteenth-century Europe.
Peter de Rivo on Chronology and the Calendar
Leuven: Leuven University Press, 2020
Peter de Rivo (c.1420–1499), a renowned philosopher active at the University of Leuven, is today ... more Peter de Rivo (c.1420–1499), a renowned philosopher active at the University of Leuven, is today mostly remembered for his controversial role in the quarrel over future contingents (1465–1475). Much less known are his contributions to historical chronology, in particular his attempts to determine the dates of Christ’s birth and death. In 1471, Peter made an original contribution to this long-standing discussion with his Dyalogus de temporibus Christi, which reconciles conflicting views by rewriting the history of the Jewish and Christian calendars. Later in his career, Peter tackled the issue of calendar reform in his Reformacio kalendarii Romani (1488) and engaged in a heated debate with Paul of Middelburg on the chronology of Christ. This book edits the Dyalogus and Reformacio and sets out their context and transmission in an extensive historical introduction.
Robert Grosseteste's Compotus
Oxford: Oxford University Press, 2019
Robert Grosseteste (1168/75-1253), Bishop of Lincoln from 1235-1253, is widely recognized as one ... more Robert Grosseteste (1168/75-1253), Bishop of Lincoln from 1235-1253, is widely recognized as one of the key intellectual figures of medieval England and as a trailblazer in the history of scientific methodology. Few of his numerous philosophical and scientific writings circulated as widely as the 'Compotus', a treatise on time reckoning and calendrical astronomy apparently written during a period of study in Paris in the 1220s. Besides its strong and long-lasting influence on later writers, Grossteste's 'Compotus' is particularly noteworthy for its innovatory approach to the theory and practice of the ecclesiastical calendar—a subject of essential importance to the life of the Latin Church. Confronting traditional computistical doctrines with the lessons learned from Graeco-Arabic astronomy, Grosseteste offered his readers a critical and reform-oriented take on the discipline, in which he proposed a specific version of the Islamic lunar calendar as a substitute for the failing nineteen-year cycle the Church still employed to calculate the date of Easter. This new critical edition of Grosseteste's 'Compotus' contains the Latin text with an en-face English translation. It is flanked by an extensive introduction and chapter commentary, which will provide valuable new insights into the text's purpose and disciplinary background, its date and biographical context, its sources, as well as its reception in later centuries.
Scandalous Error: Calendar Reform and Calendrical Astronomy in Medieval Europe
Oxford: Oxford University Press, 2018
The Gregorian calendar reform of 1582, which provided the basis for the civil and Western ecclesi... more The Gregorian calendar reform of 1582, which provided the basis for the civil and Western ecclesiastical calendars still in use today, has often been seen as a triumph of early modern scientific culture or an expression of papal ambition in the wake of the Counter-Reformation. Much less attention has been paid to the reform's intellectual roots in the European Middle Ages, when the reckoning of time by means of calendrical cycles was a topic of central importance to learned culture, as impressively documented by the survival of relevant texts and tables in thousands of manuscripts copied before 1500. For centuries prior to the Gregorian reform, astronomers, mathematicians, theologians, and even Church councils had been debating the necessity of improving or emending the existing ecclesiastical calendar, which throughout the Middle Ages kept losing touch with the astronomical phenomena at an alarming pace. Scandalous Error is the first comprehensive study of the medieval literature devoted to the calendar problem and its cultural and scientific contexts. It examines how the importance of ordering liturgical time by means of a calendar that comprised both solar and lunar components posed a technical-astronomical problem to medieval society and details the often sophisticated ways in which computists and churchmen reacted to this challenge. By drawing attention to the numerous connecting paths that existed between calendars and mathematical astronomy between the Fall of Rome and the end of the fifteenth century, the volume offers substantial new insights on the place of exact science in medieval culture.
Walcher of Malvern: 'De lunationibus' and 'De Dracone'; Study, Edition, Translation, and Commentary
Turnhout: Brepols, 2017
Walcher, the prior of Great Malvern in Worcestershire (d. 1135), is a landmark figure in the hist... more Walcher, the prior of Great Malvern in Worcestershire (d. 1135), is a landmark figure in the history of medieval science, whose work brought the Latin computistical tradition to its apex while foreshadowing the twelfth-century Renaissance in mathematical astronomy. His most famous achievement is the observation of a lunar eclipse in 1092 with the aid of an astrolabe, which is the first of its kind to be recorded in a Latin source. In spite of his renown, Walcher’s writings have never received any close scrutiny and the precise rationale and modalities behind his observations and calculations remain ill-understood. This volume contains the first complete edition of Walcher’s two known treatises (De lunationibus and De Dracone), together with an English translation and a detailed commentary. An introductory study will elucidate the background to his scientific pursuits and situate them in the intellectual and disciplinary context of the late-eleventh and early-twelfth century, when Latin astronomy underwent a transformation of lasting significance.
Leiden: Brill, Jun 9, 2014
During the later Middle Ages (twelfth to fifteenth centuries), the study of chronology, astronomy... more During the later Middle Ages (twelfth to fifteenth centuries), the study of chronology, astronomy, and scriptural exegesis among Christian scholars gave rise to Latin treatises that dealt specifically with the Jewish calendar and its adaptation to Christian purposes. In Medieval Latin Christian Texts on the Jewish Calendar C. Philipp E. Nothaft offers the first assessment of this phenomenon in the form of critical editions, English translations, and in-depth studies of five key texts, which together shed fascinating new light on the avenues of intellectual exchange between medieval Jews and Christians.
Leiden: Brill, 2012
The beginnings of scientific chronology are usually associated with the work of the great Renaiss... more The beginnings of scientific chronology are usually associated with the work of the great Renaissance philologist Joseph Scaliger (1540–1609), but this perspective is challenged by the existence of a vivid pre-modern computistical tradition, in which technical chronological questions, especially regarding the life of Jesus, played an essential role. Christian scholars such as Roger Bacon made innovative breakthroughs in the field of historical dating by applying astronomical calculations, critical exegesis, and the study of the Jewish calendar to chronological problems. Drawing on a wide selection of sources that range from late antiquity to 1600, this book uses the history of the date of Christ’s Passion to shed new light on the medieval contribution to science and scholarship.
Articles by Philipp Nothaft
Medieval Latin Christian Texts on the Jewish Calendar: Addenda and New Discoveries
Journal of Jewish Studies, 2025
This article is intended to serve as a supplement to the volume Medieval Latin Christian Texts on... more This article is intended to serve as a supplement to the volume Medieval Latin Christian Texts on the Jewish Calendar published in 2014. It provides references to previously neglected Latin texts and/or numerical tables related to the rabbinic lunar calendar, which appear in manuscripts copied between the twelfth and sixteenth centuries. Among the material covered are comments on the Jewish calendar in some recently published computus treatises of the twelfth century and a fourteenth-century Italian manuscript containing decision trees for the year-types in the rabbinic calendar. The article also documents the thirteenth- and fourteenth-century spread of Latin tables for finding the date/time of mean conjunction (molad) according to the Jewish calendar, including those contained in a work by the Franciscan John of Pershore. In addition it covers various late-medieval calendars in which conjunction times are given in the Jewish manner of dividing the hour into 1,080 ḥalakim.
Studies in Medieval and Renaissance Sources, 2025
This article presents a critical edition of what appears to
be the earliest redaction of the "Tra... more This article presents a critical edition of what appears to
be the earliest redaction of the "Translatio" of the relics of St. Bartholomew
to Benevento, which was added to the final surviving folio of Cambridge,
Pembroke College, MS 91 in northern France between ca. 839 and ca. 850.
This incomplete text has been overlooked by scholars studying the cult of
St. Bartholomew in that city as well as related hagio graphic traditions. An
examination of the text allows us to reconsider not only the beginnings of
the cult in Lombard Benevento but also the role that Duke Sicard played
in the translation of Bartholomew’s relics there. The original account was
produced in 838–839, after the arrival of the saint’s body in Benevento and
prior to Sicard’s assassination, and communicated the perception of the new cult within his entourage. Unlike other known hagiographic texts related to this "Translatio" and produced in the wake of Sicard’s death, the earliest redaction presented him as a legitimate heir to the Roman imperial principes and laid claim to the Apostolic tradition of St. Bartholomew, which is here placed on an equal footing with that of St. Peter and St. Paul.
Journal for the History of Astronomy, 2025
This short note responds to a recent article on "Occultation Records in the Royal Frankish Annals... more This short note responds to a recent article on "Occultation Records in the Royal Frankish Annals for A.D. 807: Knowledge Transfer from Arabia to Frankia?" by Ralph Neuhäuser and Dagmar L. Neuhäuser (JHA 55, no. 3). It shows that, contrary to a key claim made in this article, the presence of rules for predicting solar and lunar eclipses in manuscripts associated with the so-called Seven-Book-Computus of 809 is due to the influence of the Liber Nemroth, a text with roots in the pre-Islamic Near East.
Mediterranea, 2025
This article discusses the shared content of three interrelated astronomical manuscripts from lat... more This article discusses the shared content of three interrelated astronomical manuscripts from late medieval Italy, arguing that certain elements of this shared content trace their origins to Maghribī sources. This includes two tables of geographic coordinates with a pronounced focus on locations in North Africa as well as a gnomonic table for the latitude of Tunis. One of the coordinate tables is known to resemble an Arabic table in a zīj by Ibn al-Raqqām, who was active in Tunis, Béjaïa, and Granada in the period 1280-1315. It will be argued that a likely explanation of this knowledge transfer lies in the documented mercantile and diplomatic contacts between the Republic of Venice and Ḥafṣid Tunisia in the decades around 1300.
Annals of Science, 2025
A manuscript now in Bamberg preserves the only surviving fragment of a thirteenth-century treatis... more A manuscript now in Bamberg preserves the only surviving fragment of a thirteenth-century treatise on comets or ‘new stars’, which was written as a letter addressed by an unknown Dominican author to the Master General of his order, John of Vercelli. The present article offers the first discussion of this forgotten work, which was composed in the year after the Great Comet of 1264. Although most of the text has been lost, the inclusion of a geometrical diagram in the manuscript makes it possible to reconstruct a crucial part of its overall argument. The Dominican author was openly critical of the Aristotelian doctrine of comets as atmospheric phenomena and considered the possibility that reliable distance estimates might instead place such objects in the celestial realm. His geometrical investigation of this question is historically significant for containing the earliest known analysis of the effect of cometary distance on its observable parallax, thus anticipating aspects of Johannes Regiomontanus’s seminal '16 Problems' on comets.
Heavens: The Papacy, Astrology, and Astronomy to 1800
The Cambridge History of the Papacy, vol. 3, Civil Society, edited by Joëlle Rollo-Koster, Robert A. Ventresca, Melodie H. Eichbauer, and Miles Pattenden (Cambridge: Cambridge University Press), 2025
The papacy’s long-standing entanglements with the twin disciplines of astronomy and astrology can... more The papacy’s long-standing entanglements with the twin disciplines of astronomy and astrology can be summarized along three thematic strands. One revolves around the ecclesiastical calendar and the astronomical exigencies of the reckoning of Easter, whose historical ramifications range from late antique Easter controversies to the Gregorian reform of the calendar (1582) and the beginnings of the Vatican Observatory. Another is the more general role of popes as patrons of astronomical research as well as their more anomalous involvement in scientific censorship during the cosmological controversies of the early modern period, as exemplified by the trial against Galileo Galilei (1616/33). A third is the complex relationship between the Roman Curia and astrology, which includes episodes of patronage as much as instances of sharp anti-divinatory legislation, with the latter culminating in the trial against Orazio Morandi (1630).
Aestimatio, 2023
"Liber de wazalkora” is the title of an unpublished Latin treatise on the construction and use of... more "Liber de wazalkora” is the title of an unpublished Latin treatise on the construction and use of the planispheric astrolabe, which appears to have been compiled in southeast Germany (Bavaria) in the second half of the 12th century. It is to a large extent derived from other astrolabe sources available in the Latin West before 1100, but also contains material that has no precedent in any of the known literature. The analysis presented in this article concentrates on the Liber de wazalkora’s section on the use of the astrolabe, which is unusual for both its extraordinary length and frequently atypical astronomical content. A study of the Arabic loan vocabulary in this section leads to the conclusion that some parts of the text were derived from an unidentified Arabic source, presumably via a Latin intermediary.
Vivarium, 2024
The idea of reconciling Ptolemaic planetary theory with Aristotelian natural philosophy by imagin... more The idea of reconciling Ptolemaic planetary theory with Aristotelian natural philosophy by imagining epicycles and eccentric deferents as three-dimensional orbs or orb-segments within larger spheres is frequently associated with Georg Peurbach and his widely read astronomy textbook, the 'Theoricae novae planetarum' (1454). This article cautions against existing tendencies to overstate the originality or revolutionary force of this work by taking a closer look at the early history of the same Ptolemaic-Aristotelian compromise in a Latin European context. Using previously unpublished or unused source material from the twelfth to early fourteenth centuries, it documents the gradual spread and acceptance of an orbicular interpretation of Ptolemy’s planetary models among astronomers and university teachers.
Journal for the History of Astronomy, 2024
Two Latin sources from the years around 1300 (John of Sicily's commentary on the canons to the To... more Two Latin sources from the years around 1300 (John of Sicily's commentary on the canons to the Toledan tables and a parchment slip documenting the astronomical activities and observations of Alard of Diest) contain brief references suggesting that Parisian scholars of this period had access to a set of astronomical tables for Tunis known as tabulae Benesac. According to the argument developed in this article, the tables in question probably corresponded to a Maghribī zīj originally created by Ibn Isḥāq al-Tūnisī in c.1222. The article goes on to discuss the possible channels of transmission that could have brought these tables to Paris as well as the potential implications of this finding for the history of Latin astronomy in the late 13th and early 14th century. Attention is also drawn to the presence of eclipse-related material from the Muqtabas zīj by Ibn al-Kammād in a Northern French manuscript of the second half of the 13th century, which was independently translated from the Arabic and accordingly does not derive from the well-known translation by John of Dumpno (Palermo, 1260).
Journal for the History of Astronomy, 2024
Manuscripts in Oxford and Erfurt preserve evidence of the earliest known efforts made in Latin Eu... more Manuscripts in Oxford and Erfurt preserve evidence of the earliest known efforts made in Latin Europe to remeasure the eccentricity and maximum equation of the Ptolemaic solar model. The present article analyses and contextualizes this evidence, while also revisiting Ernst Zinner's hypothesis according to which the relevant observations were made by Alard of Diest (fl.1308).
Mediterranea, 2024
The Latin manuscript sources studied in this article jointly document the existence and erstwhile... more The Latin manuscript sources studied in this article jointly document the existence and erstwhile circulation of a highly atypical set of computational tables for planetary longitudes, coupled with extensive tables for ascensions, which served astrologers in Latin Europe as early as the 1130s. An associated text of c.1220 refers to the tables for the five planets as "combustion tables" (tabule combustionis), which reflects the way the tables in question use the time and position of the last conjunction between a planet and the Sun -- known in medieval terminology as "combustio" -- as an anchor for calculating the planet's true ecliptic longitude at a later date within its synodic period. Multiple lines of evidence suggest that the combustion tables as well as the associated solar and ascension tables originally circulated alongside the pseudo-Ptolemaic "Iudicia", an astrological work of probable Arabic origin (pre-1138). Overall, the surviving manuscript material raises the possibility that the tables and the "Iudicia" were at one point a single work that supported astrological computations and judgments at an early stage of their respective development in Latin Europe.
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Books by Philipp Nothaft
Articles by Philipp Nothaft
be the earliest redaction of the "Translatio" of the relics of St. Bartholomew
to Benevento, which was added to the final surviving folio of Cambridge,
Pembroke College, MS 91 in northern France between ca. 839 and ca. 850.
This incomplete text has been overlooked by scholars studying the cult of
St. Bartholomew in that city as well as related hagio graphic traditions. An
examination of the text allows us to reconsider not only the beginnings of
the cult in Lombard Benevento but also the role that Duke Sicard played
in the translation of Bartholomew’s relics there. The original account was
produced in 838–839, after the arrival of the saint’s body in Benevento and
prior to Sicard’s assassination, and communicated the perception of the new cult within his entourage. Unlike other known hagiographic texts related to this "Translatio" and produced in the wake of Sicard’s death, the earliest redaction presented him as a legitimate heir to the Roman imperial principes and laid claim to the Apostolic tradition of St. Bartholomew, which is here placed on an equal footing with that of St. Peter and St. Paul.