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  • On Professor Westman’s Reply to Copernicus and Astrology, with an Appendix of Translations of Additional Primary Sources1
  • N. M. Swerdlow (bio)

Professor Westman’s reply need be considered only briefly. When I received for review The Copernican Question, Prognostication, Skepticism, and Celestial Order, with its superlative commendations, I believed I had in my hands a book of surpassing erudition, the culmination of more than forty years of study by one of the world’s greatest experts on Copernicus and the astronomy and astrology of the Renaissance and early modern period. Imagine my surprise as I read this vast tome and discovered that it did not appear worthy of Professor Westman’s eminence. Still, I reviewed the book as well as I could and, leaving aside matters of opinion, concentrated upon two issues, competence and trust. Is Professor Westman competent to understand and translate his sources, and can his word for the content of these sources be taken on trust? The results of this inquiry were not favorable to Professor Westman, for his work fails in both competence and trust, rather, it is filled with error and misunderstanding, with little knowledge of the sources he cites and of the subjects, particularly astronomy and astrology, about which he writes. This was shown in the review by examining what he writes, and does not write, about his sources and subjects, and in the Appendix to the review by translating primary sources at length for comparison with what he writes. In addition, and of greater importance, the translations of these interesting texts, most never translated into English, are intended to remain useful apart from the review. [End Page 384]

Professor Westman objects that the review has “inflated minor issues of translation.” But translation is not a minor issue, for it is translation above all that shows whether sources have been read and understood. From the account of his research in his Preface, Professor Westman has had between ten and twenty years to read, understand, and translate his sources, and he does say that he has made his own translations. Yet, he does not translate a single text a fraction of the length of those in the Appendix. For even his most important sources, he provides no more than a “snippet view”, picking out some words or phrases, a fraction of their content, and often not accurately. Nor does he write an adequate exposition of his sources, both from not understanding them and from ignoring anything technical or mathematical. There is no need to repeat the evidence for this judgment in the review and its Appendix, supplemented here by another Appendix, with translations of sources Professor Westman says in his reply are very important and not mentioned in the review. Professor Westman calls the review “a futile attempt to undermine trust in the book’s evidentiary credibility and thereby to divert attention from the scope of the argument and its real objectives.” Futile attempt? Well then, read the review and its Appendix, read the pertinent sections of Professor Westman’s book, read his reply, read the additional Appendix provided here (, read everything, the closer the better, and decide for yourself. The issues, as I said, are competence and trust. Professor Westman could have addressed these by devoting his reply to translating sources of importance to his book to show that his understanding of them is correct. But he did not do so. And until he does, there is no reason to alter the judgment of the review. [End Page 385]

N. M. Swerdlow
California Institute of Technology
N. M. Swerdlow

N. M. Swerdlow is Professor Emeritus in the Department of Astronomy and Astrophysics of the University of Chicago and Visiting Associate in the Division of Humanities and Social Sciences of California Institute of Technology. His research is concerned principally with the history of astronomy from antiquity through the seventeenth century.


1. The Appendix may be found as a downloadable file at the web site for this issue of Perspectives on Science ( The original review is Copernicus and Astrology, with an Appendix of Translations of...


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pp. 384-385
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