The issue of God's grace and human freedom has been of ongoing importance to Christian theology. Muller's book examines this key point of contention between Reformed Protestants and Roman Catholicism. It also illuminates the Reformed orthodox understanding of free choice and whether modern terminology of “libertarianism” and “compatibilism” are legitimate ways to discuss Reformed viewpoints. Muller wants to “clarify the meaning and intention of early modern Reformed thought in its ecclesial, confessional, and polemical contexts, with emphasis on the writings of William Perkins and various of his predecessors and contemporaries” (1). In this, Muller succeeds quite well.

Perkins (1558–1602) was a major Elizabethan theologian whose writings were a significant theological backbone for Puritanism, in Old and New England. Perkins's background influences were Augustinian, and he drew from Continental Reformed theology, including Calvin, Bullinger, Beza, Vermigli, Zanchi, and Ursinus. Muller addresses “how a creature corrupted by sin but still endowed with free choice could be understood as predestined by God and saved solely by grace” (2). This problem of reconciling grace and freedom was not directly addressed by Calvin (or Luther) but was faced head-on by second-generation Reformers. Their language paved the way for usage by later Reformed theologians Voetius and Turretin. Perkins was a major formulator in this trajectory.

Muller describes Perkins's work in minute detail and how, ultimately, contemporary “libertarianism” and “compatibilism” are inadequate to capture the theological nuance and core of Reformed thought on grace and freedom. Muller contends that “the key to the Reformed understanding of human free will and the determinative divine operation of grace is not a compatibilist view of willing but the assumption that all rational agents act freely according to their nature, that freedom operates within the bounds of the nature, and that the nature itself must be redeemed” (5–6).

Muller's close study of Perkins moves through chapters on “Knowing and Willing in Freedom: Divine and Human”; “The Nature of the Will and Its Strength”; “Liberty and Mutability: The Strength of the Will and the Loss of Grace”; “Liberty Restored: Grace and the Will in Redemption and Glorification”; “The Harmony and Consent of Divine and Human Willing”; and a conclusion. This outline shows attention to the issue of the will and its freedom in the various conditions of humanity: created by God, sinner, regenerate, and glorified.

Underlying Perkins's presentations—as outcomes of medieval discussions between Thomists, stressing the intellect as the determinative faculty; Scotists, who saw will as prior; and those advocating liberum arbitrium as a third faculty which functions in relation to the intellect and will—Perkins, says Muller, “took a voluntarist approach that assumed the freedom of the will to choose or reject an intellective judgment, but he also viewed free choice or liberum arbitrium as residing in both faculties, intellect and will, as opposed to identifying it as a third faculty” (8–9). In this, Perkins was joined by “a large number of early modern Reformed writers” (22). Ursinus may have been “the most influential of the earlier Reformed theologies on Perkins’ thought, perhaps instrumental in pressing it in a voluntarist direction” (184). Throughout, Muller sees Perkins as providing “a basic confessional continuity with the second-generation codifiers of Reformed thought as well as discontinuities in method and nuance of argument” (184).

Muller shows Perkins and his contemporaries developed nuanced understandings of free choice and divine grace in relation to the Augustinian formulation of humanity's four states: original, sinless, but able to sin; fallen, sinful, and not able not to sin; regenerated but sinful, able to sin and not to sin; and glorified, not able to sin. Perkins's most sustained treatment was in his Treatise of God's Free Grace, and Mans Free-will. Here, Perkins claimed a twofold relation between divine and human willing: first, because willing is an analogous concept based on the image of God in humans—free human willing resembles divine willing; second, “because divine willing accounts for all that exists in the finite, created order, human willing occurs dependent on and within the compass of divine willing” (44). This twofold relation is seen in all four states of humanity. A distinctive Perkins contribution was greater elaboration of the “states” providing better clarification of Reformed views, “particularly,” says Muller, “in his differentiation between the bound choice of the state of sin in the ‘libertie of sinning’ present in the state of regeneration” (186).

Perkins did not turn to predestination as “a causal explanation” in arguing the nature of human freedom in humankind's four states. He “does not appeal to the divine decree as the efficient cause of intellective determinations or volitional acts” (186). Humans are free where to walk or what to eat. No “causal determinism explains human choice in general.” Reformed doctrine is not a thoroughgoing determinism. God's divine decree includes “the governance of contingent and free events.” These occur on the level of divine causality. But on the level of secondary causality, events occur “in and through their own causation” by the interaction of human intellect and will (187). God “guarantees the free choice of free creatures, who always must act according to their natures” (194).

In salvation, “grace regenerates the will so that in the same instant that it passively receives the grace of God it responds actively to the grace” (190). Sinful humans lack “the freedom to choose, refuse, or suspend without sin” (195). For Perkins, “God is capable both of causing the regeneration of the elect and determining their end without the removal, indeed, without any abridgement, of human freedom or coercion of the will” (191). God's grace “regenerates the will to yield a new liberty, namely, a liberty, as Perkins and others defined it, not merely to will but to ‘will well’” (193). This “grace does not remove human freedom; it renders human beings more free” (195).