by Prof. Richard W. Pogge, Ohio State University
... The one key fact of the study of Bruno's life is that we do not actually know the exact grounds of his conviction on charges of heresy. The simple reason is that the relevant records have been lost ...
Except for certain particular passages that excite our interest today, much of his work had little to do with astronomy. Indeed, Bruno was not an astronomer and demonstrated a very poor grasp of the subject in what he did write ... Much of his work was theological in nature, and constituted a passionate frontal assault on the philosophical basis of the Church's spiritual teachings ... Copernicanism, where it entered at all, was supporting material not the central thesis. This suggests that the Church's complaint with Bruno was theological not astronomical ...
Further support for the idea that Copernicanism was likely to have played only a minor role if any in his conviction comes from the contemporary record of the discussion of this idea. What many popular accounts seem to miss is that the Church did not formally condemnation Copernicanism until well after Bruno's death ...
Further, Copernicanism was not actually specifically proscribed as heretical in 1616. After Bellarmine's examination, Copernicus' De Revolutionibus and Foscarini's book (among others) were placed on the Index of Forbidden Books, the former to remain on the Index until specific, minor revisions were made (a few words deleted and some passages excised, but on the whole leaving the basic ideas intact). An official response to be sure, but still a long ways from a definitive ban on Copernicanism in general. Indeed, copies of De Revolutionibus were published in Italy after 1616 (with the prescribed revisions, of course), and the situation was sufficiently ambiguous that Galileo felt free to proceed with his work until his trial in 1633 ...
http://www.setileague.org/editor/brunoalt.htm
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