To write about Paolo Sarpi is to invite contradictions and inconsistencies. The Venetian Servite friar (1552–1623) was variously a philosopher, a political adviser, a theologian and a polemicist. Different historians have labelled him an atheist, a sceptic and a Protestant, or perhaps only a crypto-Protestant – or perhaps he was Catholic all along. Still others have seen him as a proponent of republicanism, an information-monger and a propagandist. Jaska Kainulainen's book challenges many of these interpretations. Most significantly, Kainulainen argues for ‘a greater degree of coherence to [Sarpi's] thought than has previously been the case’ (p. 6). Scholars have long disagreed over how to view Sarpi's diverse corpus of writings, and whether more weight should be placed on his private notebooks – the pensieri – or his public writings, including his consulti to the Venetian senate. Kainulainen pushes these debates aside and argues that there are discernible themes common to all of Sarpi's writings. In this intellectual biography, the author proposes that Sarpi ‘was consistent in his absolutism, anti-papism and anticlericalism, as well as in his materialism, naturalism and determinism’ (p. 7).

The book's chapters develop this argument, moving more or less chronologically through Sarpi's career. At each stage Kainulainen wants to contextualise Sarpi's thinking with that of his contemporaries. After a brief account of Sarpi's life, the author analyses Sarpi's natural philosophy, which is perhaps the book's most innovative contribution, since this area of Sarpi's thought has received less attention than others. Kainulainen convincingly describes Sarpi's links to Galileo as well as his adherence to atomism and determinism. He goes on to link Sarpi's natural philosophy with his ontology and epistemology, describing Sarpi's low view of mankind after the Fall, including humanity's limited sense perception and inability to comprehend divine causes. The author makes a strong argument for Sarpi's religiosity and his commitment to Augustinianism, against historians like David Wootton who have seen Sarpi as an atheist. For Kainulainen, Sarpi was instead a reformer, one ‘whose religiosity exceeded the limits of confessionalism’ (p. 128) – thus acknowledging Sarpi's sympathy for Protestant reformers while stopping short of calling him a Protestant himself. Kainulainen confirms Sarpi's anti-papalism and anticlericalism, though he points to Sarpi's admiration for the early Christian Church.

The last three chapters turn to Sarpi's political and ecclesiological thinking, looking especially at Sarpi in relation to Machiavelli, Bodin and Hobbes while also highlighting his critique of the early modern papacy. Kainulainen again links Sarpi's political thinking with his writing on other topics. He proposes that Sarpi's view of postlapsarian mankind directly influenced his political thinking, since Sarpi's ‘belief in man's physical and moral imperfection was conducive to the emergence of absolutistic principles in his political thought’ (p. 101). Kainulainen makes the intriguing, though not always convincing suggestion (against Bouwsma and others) that Sarpi was less a proponent of republicanism than of absolutism, arguing that the friar never referred to the myth of Venice or praised mixed forms of government in his writings.

This is a book that covers a dizzying array of complex topics. Even with so much ground to cover, though, we should take note of what is not included. Kainulainen wants to see where Sarpi fitted in and attempts to locate him among devotees of the new science like Galileo and political theorists like Bodin. However, it is equally important to consider where Sarpi did not fit in, and with whom he disagreed. Kainulainen makes a convincing argument for Sarpi's alignment with Augustinianism, which, as the author notes, was then in vogue among both Protestant and Catholic reformers. Yet the writings of Thomas Aquinas also remained influential in the sixteenth century, especially among Jesuit theorists like Sarpi's contemporaries Robert Bellarmine (1542–1621) and Francisco Suárez (1548–1617). Like its Augustinian counterpart, this Thomistic heritage also shaped contemporary political thought, and though Sarpi did not embrace this line of thinking himself, he was certainly aware of it – in fact, he spent much of his career writing against its proponents. (For instance, Kainulainen mentions in passing that Sarpi quoted from Suárez on the subject of regicide.) Unfortunately, Bellarmine, Suárez, Cesare Baronio and other ‘papalist’ thinkers are largely absent from this book. This omission is unfortunate because it distorts the broader intellectual context within which Sarpi worked, obscuring the men whom Sarpi saw as his principal rivals.

To that point, it is puzzling that Sarpi's famous polemical writings are not mentioned in a book that wants to emphasise the coherence of Sarpi's thought. Besides the pensieri (which remained unpublished during his lifetime), Kainulainen has chosen to focus on Sarpi's consulti and his overtly political treatises, and not, for example, on his Apologia per l'oppositioni fatte dall'illustriss. et reverendissimo Signor Cardinale Bellarmino alli trattati et risolutioni di Gio. Gersone (1606), to which Bellarmine responded and which was translated into English the following year. This example alone shows how Sarpi could define his political and ecclesiological thinking in opposition to a ‘papalist’ position – in this case, by defending the conciliarist tradition and criticising Bellarmine's theory of the papal potestas indirecta – as well as how Sarpi's anti-papal polemic could be adapted for a Protestant, English audience. Simply put, Sarpi's contemporaries were far more likely to know him for his polemical tracts than for his theories of natural philosophy or treatises on political theory. Both the quantity and acerbity of this polemic suggest that Sarpi was self-conscious about his position vis-à-vis other thinkers, and the present book might have benefitted from further consideration of Sarpi's position in relation to other Catholic authors. Nevertheless, this is a thought-provoking book, and Kainulainen should be praised for advancing the discussion about Fra Paolo in new directions. Anyone writing on Sarpi in the future will need to take this book into consideration.