Calvin freely acknowledged that his authority was Augustine. Consider the following quotes:
“If I were inclined to compile a whole volume from Augustine, I could easily show my readers, that I need no words but his” (Institutes, Book III, chap. 22).
“Let Augustine answer for me…” (Ibid.).
“[Augustine is the one] we quote most frequently as being the best and most faithful witness of all antiquity” (Institutes, Book IV, chap. 14).
“Augustine is so wholly with me, that if I wished to write a confession of my faith, I could do so ... out of his writings” (Calvin, “A Treatise on the Eternal Predestination of God,” trans. by Henry Cole, Calvin’s Calvinism, Grandville, MI: Reformed Free Publishing, 1987, p. 38; cited in Laurence Vance, The Other Side of Calvinism, 1999, p. 38).
WHO WAS AUGUSTINE? He was so polluted with heresy that the Roman Catholic Church has claimed him as one of its “doctors.”
Augustine was a persecutor and the father of the doctrine of persecution in the Catholic Church. The historian Neander observed that Augustine’s teaching “contains the germ of the whole system of spiritual despotism, intolerance, and persecution, even to the court of the Inquisition.” He instigated bitter persecutions against the Bible-believing Donatists who were striving to maintain pure churches after the apostolic faith.
Augustine was the father of amillennialism, interpreting Bible prophecy allegorically; teaching that the Catholic Church is the kingdom of God.
Augustine taught that Mary did not commit sin.
Augustine believed in purgatory.
Augustine was one of the fathers of the heresy of infant baptism, claiming that unbaptized infants were lost, and calling all who rejected infant baptism “infidels” and “cursed.”
Augustine exalted church tradition above the Bible and said, “I should not believe the gospel unless I were moved to do so by the authority of the Catholic Church.”
A great danger of christians following the doctrines of one man, such as Calvin, and Augustine before him, is that people become dependent upon those doctrines as systematized or 'crystalized' by that one man instead of seeking God directly in His word and letting the Holy Spirit teach us. This doesn't mean it's not good to be taught by godly men; of course it is; but we are responsible to compare everything to scripture and God promises He will teach us if we seek Him diligently in His word.
I'd like to look more at what Calvin taught as he received it from Augustine next time I post, if possible.