BornDanzig, (Gdańsk, Poland), 1571 or 1573
Bartholomew Keckermann developed a system of astronomy that was a basic outline of the Aristotelian universe, and which was widely used as a textbook.
Born to Calvinists George and Gertrude Keckermann, Keckermann studied under Jacob Fabricius at the Academic Gymnasium of Danzig starting in 1586, before moving to Wittenberg, where he enrolled at the University of Wittenberg in 1590. In 1592, Keckermann enrolled at the University of Leipzig, but after one semester he and fellow Calvinist students became unwelcome due to the death of protector Prince Christian I. Keckermann then moved to Heidelberg, where he studied from 1592 until 27 February 1595, receiving a master of arts degree. Keckermann stayed in Heidelberg and eventually held a professorship in Hebrew there, but in 1602 after writing to the Danzig City Senate about his desire to return to his native city, he was offered a position to teach philosophy in the Danzig Gymnasium. There, Keckermann worked incessantly, paying little attention to sleep or health. This led to his early death.
Known as a great pedagogue, Keckermann employed a systematic method of introducing students to subjects such as geometry, astronomy, optics, and geography. Keckermann presented his system of astronomy during lectures in 1605 and 1607. This system was first published posthumously in the Systema physicum, septem libris (1610), and later in different forms in the Systema astronomiae compendosium (1611), his Operum omnium quae extant (1614), and the Systema compendiosum totius mathematices (1617). Included in some of these works were discussions of phenomena related to astronomy such as comets and meteors, but they were placed under different systems such as physics. The commentaries of Georg Peurbach and Johann Müller (Regiomontanus) aided Keckermann in developing his system of astronomy.
Keckermann began with general information about the motions of the heavenly spheres, which he held to be material despite arguments against this position resulting from observations of the comet of 1577 showing that it traversed planetary spheres. He then treated the motions of each of the planetary spheres separately. After working through the planetary spheres, Keckermann ended his system of astronomy by giving fundamental explanations concerning time reckoning and the reasons behind the recent change from the Julian to the Gregorian calendar.
Keckermann’s syntheses of astronomical knowledge in his lectures and in the posthumous publications of his textbooks were widely used as school texts. At Harvard, Adrian Heereboord recommended Keckermann’s work as the best system of Aristotelian physics. At early seventeenth-century Cambridge, Keckermann’s works were used as standard manuals in undergraduate instruction. The English author John Milton was among the Cambridge students who were probably influenced by Keckermann’s synthesis of natural philosophy.
However, it is safe to say that Keckermann’s works were not used for their originality. He believed that tradition should prevail over unsubstantiated claims. By placing knowledge that was “rightly-ordered” before knowledge that may in fact be “true,” Keckermann stuck with the wisdom of the ancients over the moderns. For example, although he was favorable to those who denied the reality of solid celestial spheres, he could not accept their claims “because as yet no astronomical precepts have been established, through which an opinion and hypothesis of this sort can be taught in the schools.” He was waiting for the day when such precepts would be advanced through foundational textbooks such as his own. Because of his attitude, Keckermann had mixed reactions toward the work of recent astronomers like Nicolaus Copernicus and Tycho Brahe . In the margins of his personal copy of Copernicus’s De Revolutionibus he acknowledged and even praised Copernicus and other modern astronomers like Rheticus , Caspar Peucer , and Brahe. However, his system of astronomy in the Systema compendiosum followed the traditional Aristotelian model with only short references to the works of Copernicus and Brahe.
Theologically, Keckermann believed that there was a harmonious relationship between God and nature. A knowledge of physics was necessary in order to understand the scriptural accounts of creation and of natural things in the Bible such as gems, metals, and foods. His view of comets also had a theological flavor. Although he took a standard astrological position when he said that comets portend events on the Earth such as changes in empires, his causal account of why this is the case became theological. Keckermann claimed that good angels or bad demons worked with the matter of a comet to produce effects on the Earth.
The breadth of Keckermann’s work is amazing, considering how long he actually lived to create it. This probably resulted from his attitude not to be satisfied with leaving questions unanswered and at least attempting a “most probable” explanation to difficult questions.