In this erudite book, Hirai argues that the work of Renaissance medical humanists contributed to the redirection of philosophy towards what are called ‘natural questions’ (p. 3), an intellectual trend that would eventually become crucial for key figures of the seventeenth century such as Bacon, Gassendi, Hobbes, Leibniz and Newton. In particular, Hirai demonstrates that the question of the generation of living beings, the source of the formative power of life, the relation of the soul and of life to the heavenly spheres, and the transmission of the soul from parents to offspring, were problems that early modern thinkers inherited from sixteenth-century medical humanists. By examining the debates of medical humanists such as Jean Fernel and Daniel Sennert (1572–1637), the author aims to address the ‘interactions that medicine and philosophy produced at the threshold of the Scientific Revolution’ (p. 10), setting these interactions in historical and philosophical context.

There are some particularly striking intellectual connections made in this book, especially the influence of Sennert's corpuscular reinterpretation of biological generation upon Leibniz's theory of monads. In his work De spontaneo viventium ortu (On the Spontaneous Generation of Living Beings – 1636), Sennert asserted that the real origin of inferior living beings resided in the atoms of the material in which this generation took place. Living corporeal corpuscles carried the soul or seminal principle, and they were responsible for engendering life. Sennert's corpuscular reinterpretation of biological generation then contributed to the evolution of seventeenth-century embryological preformationism, which became significant to Leibniz's philosophy.

Hirai also demonstrates to what extent Sennert's idea of the seminal principle ultimately derived from the Galenic notion of formative power as reinterpreted by earlier medical humanists such as Nicolò Leoniceno and Jean Fernel. Fernel, in particular, conceptualized foetal formation as guided by a divine craftsman-like force. Jacob Schegk and Sennert, in turn, transformed this force into the world-organizing plastic agent, renamed the ‘Spirit of Nature’ by the Cambridge Platonist Henry More.

Hirai rightly states that ‘the relationship between corpuscular philosophy and the seminal principle became a vital issue in seventeenth-century matter theories’ (p. 179). Boyle in his development of corpuscularianism, and Newton in his search for a vegetative principle, had profound intellectual debts to the medical humanists of the Renaissance. Hirai's book thus elaborates upon previous research by William Newman (I am thinking particularly of his Atoms and Alchemy, 2006) that demonstrates connections between Boyle and Sennert in their respective studies of alchemy. Though the conceptual links that Hirai forges are more specific, they are arguably as important historiographically when elucidating the origins of the ‘Scientific Revolution’. One has to pay close attention when reading his book to appreciate all of the intellectual linkages, but the reward is worth the effort.

Like the medical humanists he analyses, Hirai is at pains to adhere to the principle of ad fontes, tracing ideas to their original source, and his work is careful, philologically nuanced, and balanced in argument. In a clever bit of book design, Hirai even portrays himself on the back cover in the Renaissance garb of Cornelius Gemma (1535–1578), one of the humanists he analyses. So I well understand, and sympathize with, the spirit of his book.

That said, whilst I was very happy to find in the appendix excerpts from carefully transcribed treatises in Latin by Jacopo Zabarella and Fortunio Liceti (amongst others), it would have been perfectly appropriate and helpful for Hirai to use his skills as a linguist to provide English translations for the reader. Not very long ago, many scholars could read Latin as if reading the Sunday Times, but sadly this is no longer the case.

Overall, however, this book is essential for scholars of early modern matter theory, chymistry and biological studies. I recommend it highly.