I remember engaging myself in a somewhat fierce discussion with an online Roman Catholic apologist concerning Irresistible Grace some time ago. The guy insisted upon the typical anti-Calvinist objection that if Reformed theology is true that God is absolutely sovereign in Salvation (i.e. that God effectively leads to saving faith and repentance those whom he chooses to be saved by His free grace), then men are no better than puppets who have no freedom of choice.
On the contrary, however, Calvinists insist that God's sovereignty is perfectly compatible with man having a free will. St. Augustine of Hippo, the greatest post-apostolic church father of the Christian religion and a distant mentor of Martin Luther and John Calvin, puts it this way:
"We maintain," says he, "that men are the work of God, and that no one is forced unwillingly by His power either into evil or good, but that man does either good or ill of his own will; but that in a good work he is always assisted by God's grace, while in evil he is incited by the suggestions of the devil." To this I answer, that men, in so far as they are men, are the work of God; but in so far as they are sinners, they are under the devil, unless they are plucked from thence by Him who became the Mediator between God and man, for no other reason than because He could not be a sinner from men. And that no one is forced by God's power unwillingly either into evil or good, but that when God forsakes a man, he deservedly goes to evil, and that when God assists, without deserving he is converted to good. For a man is not good if he is unwilling, but by the grace of God he is even assisted to the point of being willing; because it is not vainly written, "For it is God that works in you, both to will and to do for His good pleasure," (Philippians 2:13) and, "The will is prepared by God." (Proverbs 8:35) ~Source: St. Augustine, Against Two Letters of the Pelagians, I, Ch. 36-XVIII
Now here's what interests me. There are plenty of Romanist apologists today who falsely accuse Calvinism of doing away man's freedom of choice and human responsibility; all this while affirming Mary's supposed lifelong perfection in holiness by the sovereign preservation of God. They view Mary as someone who has been purified from every stains and corruption of original sin the very first moment of her conception, and was constantly and effectually moved by God's grace unto all holiness throughout her entire life.
Does this make Mary a puppet, too? Well, obviously, the anti-Calvinists of Rome won't apply to themselves the same line of objection they use against Calvinists who hold to Irresistible Grace. Why the double standard?