Sabine Baring-Gould 
The Christian System of Salvation and Augustinian Calvinist Predestination are in Diametrical Opposition [EPUB ebook] 

Before proceeding we must lay before the reader the Five Points established by the Synod of Dort, which put the finishing touch to Calvin’s system, and which were unanimously accepted by the Puritans of the Stuart period, were received as inspired truths by the Westminster Assembly, and which formed the basis of its Catechisms. These also constituted the groundwork of Whitefield’s teaching. We have prefixed to our account of Wesley a summary of his creed, and we must do the same before handling Whitefield himself any further. Moreover, as the same teaching, somewhat modified, was preached by the Evangelical Fathers in the Church, it deserves statement here.
We are not disposed to dispute that they had considerable justification for their teaching. They had the authority of S. Augustine and the Schoolmen of the Middle Ages. But where the error lay was in elevating into a doctrine necessary to Salvation, what was no other than a theologic speculation, a mere conjecture.