Imagine an astronomical theory that implied that every single star was over a hundred times larger than the sun? It seems absurd. And yet the evidence available to early seventeenth-century astronomers necessitated this absurdity from supporters of the Copernican theory (that the earth rotates around the sun). Such was the argument of the Jesuit, Giovanni Battista Riccioli (1598–1671), whose work Graney employs to reassess common perceptions that religious motivations were central to the rejection of Copernicanism – typified in the opposition to Galileo. Riccioli, Graney argues, ‘scientifically’ demonstrated the superiority of Tycho Brahe's system (in which the sun rotates around a central stationary earth, and the planets around the mobile sun), appealing to the lack of observed stellar parallax and apparent stellar volume – caused by an artefact of early modern telescope technology.

Seventeenth-century Roman Catholic discourse accepted the possibility that Scripture could speak figuratively regarding the motion of the sun and the stability of the earth, but only if the evidence from the natural world clearly demonstrated it. Yet, as Graney portrays Riccioli's argument, setting aside all biblical and ecclesiastical authority, the balance of ‘scientific’ evidence weighed against the sun's motion, and thus made it both philosophically and hermeneutically logical to take the plain meaning of Scripture. Moreover, Graney argues, in their appeal to divine power to explain massive star sizes, Copernican astronomers were just as dependent, if not more so, on religious justification for their astronomical theory as anti-Copernicans.

Graney's account of Copernican recourse to divine fiat and anti-Copernican experimental and observational rigour makes an excellent case for the complexity involved in investigating the natural world – both now and in the past – and the relationship between such investigation and theological motivations. However, his characterisation of the Copernicans’ appeal to divine power as a ‘religious’ (as opposed to ‘scientific’) argument fails to capture the degree to which all seventeenth-century natural philosophers (unlike modern scientists) framed the natural world as created by God. Thus Copernican invocation of divine power –while making reference to biblical sources – would not have been received as necessarily grounded in biblical or ecclesiastical authority. Such arguments were still within the realm of philosophy and therefore differed categorically from theological arguments drawn from scriptural exegesis. Appealing to God's power to justify apparent absurdities in the natural world resulting from the Copernican theory was not of the same order as applying hermeneutical principles – the plain meaning of the text or the authority of previous interpreters – to a given passage, which then resulted in a specific interpretation of the natural world (geocentrism). None the less, as Graney admirably demonstrates, the heart of Riccioli's argument appealed neither to divine power nor to scriptural authority, but relied on the empirical evidence available at the time.

Setting aside all authority provides easy access into the historical complexity of seventeenth-century astronomy and religious discourse, dispelling popular myths regarding the religious basis for anti-Copernican resistance. This book therefore forms a useful supplementary text to undergraduate courses on the history of science and religion.