John Robert Christianson. On Tycho's Island: Tycho Brahe and His Assistants, 1570-1601.

Cambridge and New York: Cambridge University Press, 2000. xii + 362 pp. + 6 col. and 64 b/w pls. index. illus. gloss. bibl. $35 (cl), $22 (pbk). ISBN: 0-521-65081-X (cl), 0-521-00884-0 (pbk).

One unfortunate lacuna in the history of the natural sciences in the Renaissance has been the relative paucity of literature on the Danish astronomer Tycho Brahe (1546-1601) compared to figures like Copernicus, Kepler, Galileo, and Newton. John Christianson has attempted to fill that gap by providing us with the second substantial treatment of Tycho's work in a decade. Victor Thoren's 1990 biography The Lord of Uraniborg: a Biography of Tycho Brahe (Cambridge University Press), to which Christianson also contributed, described an observer who turned astronomical data into a cosmological theory which stood between Copernicus and Galileo as a formidable alternative to heliocentrism. Like Thoren, Christianson challenges the centuries-old portrayal of Tycho as a hardnosed empiricist which was initiated by Tycho's first biographer, Pierre Gassendi, in the seventeenth century. Gassendi's biography had the infelicitous effect of extracting Tycho the man from his original social and intellectual setting.

If Thoren's book showed a skilled theorist who could reduce and synthesize data in a coherent manner, Christianson's volume shows a Tycho who skillfully used the patronage system to advance the cause of astronomy. From his knowledge of social networks, Tycho built the first observatory in early modern Europe. The physical and social structures around Tycho reflected his wide-ranging ideals as he sought to discover the true structures of the universe. In his castle of Uraniborg, Tycho and his assistants studied the stars from the observatory above while his chemical researches in the cellar below sought to elucidate the inner connections of minerals.

The main thread running through the book is Tycho's craft in organizing one of the most effective research programs of early modern science. His cadre of assistants, called his familia, provided some of the most systematic observational data to emerge from the Scientific Revolution. Christianson's merit, however, lies in his heavy contextualization of this scientific research. One such context was Brahe's hermetic Neoplatonism which is reflected in the poetry of friendship and the reciprocal exchange of gifts and favors taking place between equals. The ideal of Platonic friendship is addressed in chapter 3 where Christianson argues that the poetry of amicitia should be seen as an integral part of Tycho's astronomical program "because it could literally alter the physical universe" (47).

Exploring this Neoplatonism forms one of the most important aspects of Christianson's contribution because until quite recently historians of science have largely ignored this context for Tycho's ideas. Drawing on the work of certain Americans (e.g., Shackelford) and Scandinavian scholars, the author points to a richer pattern which unites diverse aspects of Tycho's life and thought previously passed over. For example, in his letters to other European astronomers, Tycho occasionally criticizes other cosmological ideas as not being deep enough (penitus). These remarks have been ignored largely because historical scholarship has seen Tycho as tied to Aristotelian ideas. Take the motion of the earth as an example. Now, with an understanding of the role of Neoplatonism in Tycho, it no longer possible to say that he opposed the motion of the earth simply on Aristotelian grounds, for he had a more profound view of the relation of the cosmos to humanity. For Tycho, as for Ficino and other Neoplatonists, "amor permeated the universe, charging everything with life" (50). Human beings stood as microcosms of the whole in which there were real connections between the universe and human life, connections which held implications for the moral dimension of nature and humanity.

Taking us well beyond Gassendi's anachronistically selective biography, Christianson offers a finer sense of the wider social and intellectual context of latesixteenth-century astronomy and thereby takes us back, more than ever before, to the historical Tycho. Future Tychonic studies will be obliged to integrate descriptions of astronomy into more textured accounts of Tycho's own hermetic Neoplatonism. Labore facto, multa agenda.

KENNETH J. HOWELL

The University of Illinois 

Urbana-Champaign