For those of us with Calvinist or semi-Calvinist leanings we are often guilty of minimizing the importance of prayer. Too often I have noticed that many Calvinist have become more or less predeterminist. It is as if prayer were a charade rather than a genuine appeal to a heavenly King who can hear our request. To this I find the words of Origen in his work On Prayer valuable:
If our free will is in truth preserved with innumerable inclinations towards virtue or vice, towards either duty or its opposite, its future must like other things have been known by God, before coming to pass, from the world’s creation and foundation; and in all things prearranged by God in accordance with what He has seen of each act of our free wills. He has with due regard to each movement of our free wills prearranged what also is at once to occur in His providence and to take place according to the train of future events. God’s foreknowledge is not the cause of all future events including those that are to have their efficient cause in our freewill guided by impulse.
Even though we should suppose God ignorant of the future, we shall not on that account be incapacitated for effecting this and willing that. Rather it ensues from His foreknowledge that our individual free wills receive adjustment to suit the universal arrangement needful for the constitution of the world. If, therefore, our individual free wills have been known by Him, and if in His providence He has on that account been careful to make due arrangement for each one, it is reasonable to believe that He has also pre-comprehended what a particular man is to pray in that faith, what his disposition, and what his desire.
That being so, in His arrangement it will accordingly have been ordained somewhat after this wise: This man I will hear for the sake of the prayer that he will pray, because he will pray wisely: but that man I will not hear, either because he will be unworthy of being heard, or because his prayer will be for things neither profitable for the suppliant to receive nor becoming me to bestow: and in the case of this prayer, of some particular person, let us say, I will not hear him, but in the case of that I will. (On Prayer, IV)
Origen sounds like someone who holds to a “middle knowledge” understanding of God’s predestinating work. He knows God sees ahead and knows all things but he acknowledges that this foreknowledge allows God to foresee and react rather than merely predetermine and dictate. Therefore, although God knows our prayers before we pray, and although God may already have determined His response to those prayers, this does not mean that those prayers are meaningless. For if we never say those prayer those prayers never really happen, God never foresees those things which do not happen, and He cannot respond to something that never occurred.
the archives near Emmaus 
Brian, wasn’t Origen a universalist? If so, then the ability to sway God into action is clearly when in his realm of understanding.
Joel,
Actually I am not so sure that Origen was a universalist. First, some Origen scholars have argued that any statements he made in that direction were more of an academic exercise than his theological position. Somewhat like writing an article and submitting it to one’s peers for feedback to clarify thinking. Second, it appears that the Bishop of Alexandria at that time and others who opposed Origen both before and after his death often made statements about Origen’s doctrine that were more myth than truth. This does not mean that Origen did not believe in some sort of universal salvation, but I tend to think it was his enemies who leave us with this impression of him.
Brian, I am under the impression that Origen’s bishop supported him. Further, it would seem to me from a cursory examining of Origen’s statements that he was indeed a univerisalist.
With that said, I believe that you are correct about Origen’s enemies and the nature of their myth.
He received support from some patrons and he found favor with the bishops in Caesarea but he was not popular with his bishop while in Alexandria, Demetrios. Demetrious apparently went after Origen energetically up until his death and others followed this traditions. Also, we know he because less and less popular over the next couple hundred years as various debates arose and various people used his writings as part of their arguments. So all I am saying is that I am not sure Origen taught all that was attributed to him.