Richard Muller is well known for his seminal contributions to the study of early modern Reformed theology. His most recent work builds upon the work preceding it, Divine will and human choice: freedom, contingency, and necessity in early modern Reformed thought (Ada, Mi 2017). There Muller argued that early modern Reformed thought featured substantially different accounts of the relationship between the determinations of the divine will and human free agency than can be described in post-Enlightenment categories. Rather than holding to ‘compatibilism’ (i.e. that a libertarian conception of human free will is compatible with a determinist account of creaturely causality), early modern Reformed thinkers described human free choice in terms of ‘synchronic contingency’, meaning that human agents have genuine power of contrary choice in every particular moment. Muller's work represents one side of an ongoing debate on the nature of early modern Reformed views of human will and divine sovereignty, in many ways a debate which revolves around differing disciplinary approaches. Some modern philosopher-theologians, most notably Paul Helm, have sought to describe early modern Reformed theologians in compatibilist terms. In contrast, Muller engages the issue as an intellectual historian, claiming that Helm and others have distorted early modern Reformed theology on these issues by framing them anachronistically. The present work goes a long way towards demonstrating that discussing early modern Reformed thought in terms of libertarianism, determinism and compatibilism leads to deep misunderstanding, and contributes to the widespread misconception that early modern Reformed theology (or ‘Calvinism’) was deterministic or fatalistic in character. Muller convincingly demonstrates that this was not the case.

Grace and freedom focuses on the teaching of the English Reformed theologian William Perkins (1558–1602), and his treatment of the relationship between free choice and divine grace. Perkins was the most influential English Reformed theologian of his day. He was deeply influential upon seventeenth-century Puritanism (both in England and New England) and upon Reformed theology as a whole. Muller sets Perkins's work in a broad intellectual context, setting his views in relation not only to immediate precursors and influences such as Vermigli, Ursinus and Zanchi, but also to succeeding Reformed theologians. This offers the reader a sense of the broad agreement that existed among early modern Reformed thinkers on these themes, making it clear that Perkins was not an isolated figure, but can be regarded as broadly representative.

In this work Muller takes up several crucial issues unaddressed in the previous book, particularly the nature of human willing in relation to sin, salvation and divine grace. Perkins dealt with these themes in several works with considerable sophistication and depth. Muller's discussion is framed in the same way that Perkins framed it: according to Augustine's taxonomy of the four states of man as created, fallen, redeemed and glorified. Muller spends considerable time expounding the faculty psychology of Perkins and his contemporaries, since this is where the effects of each state of man are most acutely manifested with respect to human agency. He offers a nuanced discussion of early modern Reformed views of faculty psychology, which he describes as variously falling on a spectrum between moderate Thomist intellectualism and moderate Franciscan voluntarism. Early modern Reformed thought on the freedom of the will turned on the assumption that all rational beings act freely according to their nature, and not on the notion that all the acts of created beings are determined to one end. Thus, the central issue of human free choice with respect to salvation is whether one's nature may will supernatural goods. For Perkins, whilst fallen nature can freely will, it must be redeemed before it can will well with respect to God.

One of the most important contributions of Muller's book is his discussion of divine concurrence (chapter vi). Whereas modern descriptions of the Reformed view of divine sovereignty often assume a deterministic account of creaturely causes, Muller demonstrates that for Perkins and his Reformed contemporaries the fundamental point of reference was the distinction between primary and secondary causality. God is the transcendent primary cause of all things, directing them to their predetermined ends, yet precisely by decreeing that they operate according to their own inherent natures. That is, secondary causes genuinely operate according to their own natures (along with all the contingencies this entails) rather than being inherently determined. In the case of human beings, this entails acting according to the rational free will inherent to human nature. There is more to this than can be summarised here, but essentially Perkins argues that God so orders created causes that they are determined by the necessity of God's will at the level of primary causality, but simultaneously remain free and contingent at the level of secondary causality. Perkins and his contemporaries did not conceive of secondary causality as deterministic, nor of divine causality as overriding or operating in competition with creaturely causes.

Muller's argument could have been strengthened by engaging Perkins's early polemical treatise against astrology, A resolution to the countryman proving it unlawful for him to buy or use our yearly prognostications (1585). In this work Perkins set out to debunk both the religious acceptability and the internal logic of ‘judicial astrology’, the art of astrological prediction. One of the main points of Perkins's argument is that, in order to function, astrology must assume a deterministic account of secondary causality. This cannot be true, he reasons, since it would undermine the unquestionable reality of human free agency. In short, Perkins's polemic against astrology assumes that any deterministic account of secondary causality necessarily contradicts the notion of human free will. This all but proves Muller's thesis. William Perkins was not a ‘compatibilist’ asserting the harmony of determinism and human free will, rather he believed that these factors were strictly incompatible. Perkins's account of divine sovereignty instead rested on the distinction between primary and secondary causality.

This is a challenging and important book. Any historian who wants to discuss early modern Reformed thought competently will need to familiarise themselves with the conceptual landscape that Muller so ably maps out.