Calvinism answers the charge this it is unfavorable to good morality, not merely by opposing reason against reason, but by putting facts of world-wide reputation over against these fictitious claims. It simply asks, what rival fruits can other systems oppose if we point to the achievements of the Protestant leaders of the Reformation period, and to the high moral earnestness of the Puritans? Luther, Calvin, Zwingli, and their immediate helpers were all thorough-going "Calvinists," and the greatest spiritual revival of all time was brought about under their influence. Those in England who held to this system of faith were so very strict regarding purity of doctrine, purity of worship, purity of daily life, that by their very enemies, who thus were their best witnesses, they were called "Puritans." The Puritans in England, the Covenanters in Scotland, and the Huguenots in France, were men of the same religious faith and of like moral qualities. That the system of Calvin should have developed precisely the same kind of men in each of these different countries is proof of its power in the formation of character.
Loraine Boettner, The Reformed Doctrine of Predestination, pg 279