I remember where I heard about Calvinism! It was during my studies of criminology and the early modern philosopher, Max Weber, who penned a study of protestant churches in Europe, a note from the commentary:
Weber traced the origins of the Protestant ethic to the Reformation, though he acknowledged some respect for secular everyday labor as early as the Middle Ages. The Roman Catholic Church assured salvation to individuals who accepted the church's sacraments and submitted to the clerical authority. However, the Reformation had effectively removed such assurances. From a psychological viewpoint, the average person had difficulty adjusting to this new worldview, and only the most devout believers or "religious geniuses" within Protestanism, such as Martin Luther, were able to make this adjustment, according to Weber.
In the absence of such assurances from religious authority, Weber argued that Protestants began to look for other "signs" that they were saved. Calvin and his followers taught a doctrine of double predestination, in which from the beginning God chose some people for salvation and others for damnation. The inability to influence one's own salvation presented a very difficult problem for Calvin's followers. It became an absolute duty to believe that one was chosen for salvation, and to dispel any doubt about that: lack of self-confidence was evidence of insufficient faith and a sign of damnation. So, self-confidence took the place of priestly assurance of God's grace.
Worldly success became one measure of that self-confidence. Luther made an early endorsement of Europe's emerging labor divisions. Weber identifies the applicability of Luther's conclusions, noting that a "vocation" from God was no longer limited to the clergy or church, but applied to any occupation or trade.
However, Weber saw the fulfillment of the Protestant ethic not in Lutheranism, which was too concerned with the reception of divine spirit in the soul, but in Calvinistic forms of Christianity. The trend was carried further still in Pietism. Baptism diluted the concept of the calling relative to Calvinists, but other aspects made its congregants fertile soil for the development of capitalism--namely, a lack of paralyzing ascetism, the refusal to accept state office and thereby develop unpolitically, and the doctrine of control by conscience which caused rigorous honesty.
The "paradox" Weber found was, in simple terms:
* According to the new Protestant religions, an individual was religiously compelled to follow a secular vocation with as much zeal as possible. A person living according to this world view was more likely to accumulate money.
* The new religions (in particular, Calvinism and other more austere Protestant sects) effectively forbade wastefully using hard earned money and identified the purchase of luxuries a sin. Donations to an individual's church or congregation was limited due to the rejection by certain Protestant sects of icons. Finally, donation of money to the poor or to charity was generally frowned on as it was seen as furthering beggary. This social condition was perceived as laziness, burdening their fellow man, and an affront to God; by not working, one failed to glorify God.
As per usual, it seems you know less about your own theology than the atheist.