The Catholic Dictionary defines Predestination..........................
In its widest sense, predestination coincides with Divine Providence and God’s government of the world. Guided by His infallible prescience of the future, God from eternity fore-ordained the events that occur in time, and thus destined all things beforehand to their appointed end. In its strict and theological sense, predestination signifies the supernatural providence of God, immutably decreeing and efficaciously promoting the eternal salvation of rational creatures. It implies two essential elements: God’s infallible foreknowledge (praescientia) of the future, and His immutable decree (decretum) of eternal happiness. God sincerely wills all rational creatures to be saved, and to that end He provides them with means at least remotely sufficient for the attainment of eternal salvation; yet He does not predestine every one to life eternal, but only those in whom He sees fulfilled the unalterable conditions laid down by Himself. “For whom he foreknew, he also predestined to be made conformable to the image of his Son.” (Romans 8 ) These only are His elect, and of them no one is ever lost (John 10). In its full or adequate meaning, predestination refers to both grace and glory as a whole, and in this sense it is defined by Saint Thomas as “the foreordination of grace in the present, and of glory in the future.” It not only includes a divine election to glory as the end, but also to grace as the means, the vocation to faith, justification, and final perseverance inseparably connected with a happy death. It is with this adequate predestination that the real dogma of eternal election is exclusively concerned. Predestination is objectively certain and immutable; but without a special revelation to that effect, no one in this life can know for certain whether he is among the predestined. Hence the admonition of Saint Peter: “Wherefore, brethren, labour the more, that by good works you may make sure your calling and election.” (2 Peter, 1)
That is short and to the point. That is not someones personal opinion as are most of the comments contributed here.
Even shorter is the second sentence which explains everything:
Guided by His infallible prescience of the future, God from eternity fore-ordained the events that occur in time, and thus destined all things beforehand to their appointed end.
Somewhere I read someone explaining that as God has already seen the movie, therefore he knows everything that is coming up. He does not have to change the movie, there are no surprises, no change. Just the same as if one of us had seen a movie, and all the others had not. The one would know everything that is coming from the beginning, and nothing need to be changed.
Here is St. Augustine:
Before all decision to create the world, the infinite knowledge of God presents to Him all the graces, and different series of graces, which He can prepare for each soul,
along with the consent or refusal which would follow in each circuмstance, and that in millions of possible combinations ... Thus, for each man in particular there are in the thought of God, limitless possible histories, some histories of virtue and salvation, others of crime and damnation; and God will be free in choosing such a world, such a series of graces, and in determining the future history and final destiny of each soul. And this is precisely what He does when among all possible worlds, by an absolutely free act, he decides to realize the actual world with all the circuмstances of its historic evolutions, with all the graces which in fact have been and will be distributed until the end of the world, and consequently with all the elect and all the reprobate who God foresaw would be in it if de facto He created it." [The Catholic Encyclopedia Appleton, 1909, on Augustine, pg 97]