Renaissance Science and its Medieval Antecedents

Sacrobosco, Johannes de (ca. 1195 – ca. 1256 A.D.); Regiomontanus, Johannes (1436-1476); Peurbach, Georg von (1423-1461)

Sphaera mundi [with] Johannes Regiomontanus: Disputationes contra Cremonensia deliramenta [and] Georg von Peurbach: Theoricae novae planetarum.

Venice: Erhard Ratdolt, 6 July 1482


Quarto: 19.5 x 14.3 cm. 60 lvs. Collation: a-g8, h4. 30-31 lines, Gothic type


Bound in fine 20th c. dark green crushed morocco with the gilt monogram and armorial device of the noted collector George Abrams. Leaf a2 is printed in red and black and has two very fine decorative initials on black ground. There is a full-page woodcut of an armillary sphere on leaf a1 verso and about 40 diagrams (many half-page) in the text, 8 of which are hand-colored in a green, yellow or red wash). This is handsome copy with a little bit of marginal foxing and a few marginal notes in an early hand.

A fine copy of Erhard Ratdolt’s beautiful printing of Sacrobosco’s “Sphere”, the core astronomical textbook from the Middle Ages to the early 16th century. This edition is the first to include key texts by two of the most influential 15th c. astronomers: Johannes Regiomontanus and Georg Peurbach.

Working in the vein of the Renaissance humanists, Peurbach and his student Regiomontanus sought out the extant scientific writings of antiquity, the classical foundations of medieval European and Arabic science. Both men gleaned what they could from ancient authorities but more importantly, moved the science forward, adjusting, correcting, and often discrediting their ancient and medieval predecessors, while performing new scientific investigations of astronomical phenomena. These investigations led to important innovations, placing Renaissance astronomy on a new path.

The first of the two supplemental texts in this volume, Peurbach’s “Theoricae Novae Planetarum” (New Theories of the Planets), eventually came to replace Sacrobosco’s “Sphere” and another 13th c. text, the “Theorica planetarum communis” (Universal Theory of the Planets), attributed to Gerard of Cremona. Composed about 1454, Peurbach based his “Theoricae” on the familiar teachings of Ptolemy, Al-Battani, Al-Farghani and caliph Al-Mammun’s astronomer, whose name is unknown. The word “novae” in the title is not meant to refer to a completely new theory but only to emphasize that this work is a compilation of the latest contemporary scientific knowledge. “Following Arab astronomers, Peurbach added trepidation to Ptolemy's six motions of the celestial spheres and substituted solid crystal spheres for the hypothetical circles employed in Ptolemy's ‘Almagest’.” (Stillwell, Awakenings).

In the final text in this volume, “Disputationes contra Cremonensia deliramenta” (Arguments against the Errors of [Gerard of] Cremona), Peurbach’s student Regiomontanus offers a critique of Gerard’s aforementioned “Theorica”, and demonstrates the superiority of Peurbach’s “Theoricae novae.” Adopting the form of a dialogue between ‘Viennensis’ (the “man from Vienna”, representing Regiomontanus) and ‘Cracoviensis’ (“The one from Krakow”, representing Martin Bylica of Ilkusch), Regiomontanus used geometrical proofs, often supplemented by diagrams, to refute specific claims in the earlier “Theorica.” In the course of his critique, Regiomontanus -renowned for the accuracy of his own predictive tables and calendars- also makes corrections to Gerard’s planetary tables.

Sacrobosco’s “Sphere”:

“Sacrobosco’s fame rests firmly on his ‘De Sphaera’, a work based on Ptolemy and his Arabic commentators, published about 1220 and antedating the ‘Sphaera’ of Grosseteste. It was quite generally adopted as the fundamental astronomy text, for often it was so clear that it needed little or no explanation. It was first used at the University of Paris. There are four chapters to the work. Chapter one defines a sphere, explains its divisions, including the four elements, and also comments on the heavens and their movements. The revolutions of the heavens are from east to west and their shape is spherical. The earth is a sphere, acting as the middle (or center) of the firmament; it is a mere point in relation to the total firmament and is immobile. Its measurements are also included. Chapter two treats the various circles and their names- the celestial circle, the equinoctial, the movement of the ‘primum mobile’ with its two parts, the north and south poles, the zodiac, the ecliptic, the colures, the meridian and the horizon, and the Arctic and Antarctic circles. It closes with an explanation of the five zones. Chapter three explains the cosmic, chronic, and heliacal risings and settings of the signs and also their right and oblique ascensions. Explanations are furnished for the variations in the length of days in different global zones namely the equator, and in zones extending from the equator to the two poles. A discussion of the seven climes ends the chapter. The movement of the sun and other planets and the causes of lunar and solar eclipses form the brief fourth chapter.” (Dictionary of Scientific Biography)

ISTC ij00405000; BMC V 286; Goff J405; Hain-Copinger 14110