What is the difference between Calvinism and Reformed theology?

Calvinism strictly deals with soteriology. Reformed theology deals with other things outside of just salvation. I prefer to refer to calvinism as the Doctrines of Grace.

Yes

@CM said:

Let's begin with the basics on this matter:

1. One of the legacies of Calvinism is a strong emphasis on Christian education.
2. Prayer and praise are stressed in Calvinistic ethics.
3. The doctrine of predestination is deeply embedded in Calvinism.
4. Careful critics charge Calvinism as being at the foundation of some of our modern capitalistic abuses. Calvinists believe and have demonstrated that the church was organized to reign, and is entitled to material power. 

Evangelical Calvinism is the theological tree of most Evangelicals although some Evangelicals try to graft some branches to the Arminian tree. For example, splitting the Evangelicals today is the “Lordship/no-Lordship salvation” controversy. Though both sides are admittedly predestinarians. When one reads what John F. MacArthur, Jr (the leading representative of Lordship salvation) teaches and then read Zane Hodges and Charles Ryrie (leading spokesmen for no-Lordship salvation), one hears echoes of the same issues that Paul faced in the first century, and every other church leader from Paul’s day to ours (See MacArthur especially chapter two: “A Primer on the ‘Lordship Salvation’ Controversy”).

The Calvinism tree has its roots in a partial picture of God—God only as Sovereign. But sovereign in such a way that all that happens in this world is fore-ordained or predestinated. Thus, only some men and women are elected to be saved; others are not, they go to an eternally burning hell. The idea of human responsibility is eliminated—God wills the future for everyone because no one can possibly thwart God’s will. Calvinism is rooted in Augustine's theology. This theology is considered by many as antiquity’s greatest theologian and to whom Roman Catholicism is also greatly indebted. For the latest and most inclusive biography of Augustine, see O’Donnell.

Augustine’s logical but ill-conceived presuppositions began with his huge major premise of the Sovereignty of God that led to his innovative notions concerning original sin and man’s total depravity. Roger Olson summarized:

These notions were manifested in those who followed him from the sixth century A. D., through Aquinas and into the Reformation, to our day. Probably the greatest phenomenon in Christian church history has been the magisterial role that Augustine has played in his development of the original sin notion. None of the Latin fathers before him taught that moral sin was somehow transmitted to offspring:

• -- The Eastern church never bought into Augustine’s notions. Irenaeus (c.144- c 202), the church’s first systematic theologian, clearly avoided Augustine’s later conclusions.
• -- Julian and Pelagius, Augustine’s contemporaries, countered his biblical exegesis regarding his use of Romans 5 especially, as all previous church fathers had interpreted that chapter and other texts Augustine had used.
• -- Pelagius was equally wrong in opining that each person is born with a clean sheet and not born with inherited weaknesses and liabilities, each person able to make moral decisions without prevenient (God-initiated) grace. Because of Augustine’s immense political, oratorical and philosophical skills, he became the recognized chief architect of orthodoxy in the Western Church.
• --Augustine’s system of theology is reflected in Calvinism, which Evangelical Protestantism generally holds in common.

I hope this helps. CM

SOURCES:

• -- See John F. MacArthur, Jr., Faith Works, the Gospel According to the Apostles (Dallas: Word Publishing, 1993
• -- James. J. O’Donnell, Augustine (HarperCollins Publishers, 2005), 1-396
• -- Roger Olson, The Story of Christian Theology: Twenty Centuries of Tradition and Reform (Downers Grove, IL: Inter-Varsity Press, 1999), 530

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Reformed Theology

1. Reformed theology sees the new birth as God’s irresistible gift to those chosen for salvation—immediately changing sinners from fallen (can only sin) to redeemed (righteousness is natural).
2. Reformed theology with its new emphasis on law and grace, faith and the Holy Spirit, in their rhetorical theories. 
3. "Covenant Theology" is sometimes called federal theology. This system describes the relationship between God and man in form of covenants. It played a dominant role in Reformed theology of the seventeenth century, especially among the Puritans. Also, It was on the basis of Reformed theology that the foundation of apartheid in South Africa was laid. 

Background:

• Reformed theology has distinguished between "original sin" and "indwelling sin" in Rom 7, the latter being what remains of the former once regeneration has taken place. Shedd's "indwelling sin" that the principle of sin in the members is enfeebled by regeneration and remains in a mortally wounded condition which allows for Christian victory (See Shedd). For a fuller understanding to the entire question of indwelling sin from a Reformed standpoint, see Owen and Owen.

The first of the Reformed theologians:

• Ulrich (Huldrych) Zwingli (1484-1531).

For help in understanding Zwingli and his thought, see: 

• Samuel Macauley Jackson, Huldreich Zwingli (New York: G. T. Putnam's Sons, 1901). 
• Gottfried W. Locher, Huldrych Zwingli in Neuer Sicht (Ztlrich: Zwingli Verlag, 1969).
• G. R. Potter, Zwingli (London: Cambridge University Press, 1976)

John Calvin (1509-1564) [well-known spokesman]

• The differences between these two Reformers (Zwingli/ John Calvin) and Luther on original sin were relatively minor. The question of what man lost at the Fall has continued to be a central question for theology (as this study has shown). The medieval theologians saw Adam losing the donum superadditum. The Reformers understand this question more clearly in the ' context of the Biblical expression, "image of God" (imago Dei). Luther, in his view of sin as an orientation toward God, held that man has lost the imago Dei when he is out of relationship. Reformed theology held that imago Dei is not annihilated but horribly deformed. See Dictionary of Christian Theology, s.v. "Doctrine of Man," by William Hordern

All three were fundamentally Augustinian, but each in his own way made what adjustments he felt necessary to bring that doctrine into more consistent expression with Scripture.
 Zwingli understood sin to be motivated by a desire to be equal with God; hence the root of sin is to be found in egoism.—(Gonzalez, History of Christian Thought, 3:69-70).

However, Zwingli was reticent to speak of man's state in quite so extreme a fashion as Luther had, emphasizing man's present condition rather as:

• A misfortune than a fault, a disease more than sin  
• An infirmity and defect (Seeberg) 
• A sickness (morbus) or
• Inborn weakness, i.e., an inescapable proneness to sin.

He could say that this condition is not improperly called sin 6 and yet it is not to be seen as worthy of damnation.

In contrast to Luther and Calvin, he held back when it came to a radical statement of original sin as real sin inherent in human nature.  

• Man is prone to sin and unable to escape, but corruption is not properly called sin.  
• The Reformed theology sees "man not as being placed in eternal bliss from the beginning, but as being placed in such a way that he might attain to eternal bliss"  (See Vos).

G. C. Berkouwer was a leading mind in Reformed theology in the twentieth century.

I hope this is not too much. Truth found truth shared. CM

SOURCES:

• W. G. T. Shedd, Dogmatic Theology, 2:212ff.
• W. G. T. Shedd, Commentary on Romans (n.p.: Charles Scribner's Sons, 1879; reprint ed., Grand Rapids: Baker Book House, 1980), pp. 216ff. 
• John Owen, Indwelling Sin in Believers (reprint ed., Grand Rapids: Baker Book House, 1979).
• Charles Owen, Commentary on the Epistle to the Romans, rev. ed. (1886, reprint ed., Grand Rapids: Wm. B. Eerdmans Publishing Co., 1980), pp. 236-237.
• B. B. Warfield, Biblical and Theological Studies, ed. Samuel G. Craig (Philadelphia: Presbyterian and Reformed Publishing Co, 1968), p. 165.
• Reinhold Seeberg, Text-Book of the History of Doctrines, trans. Charles E. Hay, vol. 2 (Grand Rapids, MI: Baker, 1966), 2:309.
• Otto W. Heick, A History of Christian Thought, 2 vols. (Philadelphia: Fortress Press, 1965), 1:359. 
• G. R. Potter, Zwingli (London: Cambridge University Press, 1976), pp. 320, 336
• Samuel Macauley Jackson, Huldreich Zwingli (New York: G. T. Putnam's Sons, 1901), p. 377. 
• Geerhardus Vos, Redemptive History and Biblical Interpretation: Shorter Writings of Geerhardus Vos, ed. Richard B. Gaffin, Jr. (Phillipsburg, NJ: Presbyterian and Reformed Publishing Co., 1980) A good source regarding a historical survey of the covenant.