Eire shows that as the Reformation progressed the primary focus of the Reformers became upholding God's sovereign prerogative in worship -- what today is called the regulative principle of worship. This book demonstrates the extent of the Reformers' clear condemnation of Arminianism in worship (i.e. will-worship [Col. 2:23]) in rejecting all elements of worship that did not have Scriptural warrant. Regarding Calvin's On the Necessity of Reforming the Church Eire notes, "Calvin speaks about the nature of worship and about the seriousness of the sin of idolatry in his 1543 treatise, On the Necessity of Reforming the Church, where he concentrates on the significance of worship for the Christian religion. Calvinâ€™s argument, as indicated by the title of the treatise, is that the Church had reached such a corrupt state that its reform could wait no longer. The most significant aspect of corruption singled out by Calvin is the perversion of worship, and it is in explaining this issue that he set forth the basis for his attack on idolatry." (War Against the Idols, p. 198).
This book's teaching regarding the Reformers (and their view of the Scriptural law of worship) is as applicable today as it was in the days of the first Reformation.