The implicit argument here is that if prayer is to be possible at all man must have the power of self-determination. That is, all man's decisions must ultimately belong to himself, not God. For otherwise he is determined by God and all his decisions are really fixed in God's eternal counsel. Let's examine the reasonableness of this argument by reflecting on the example cited above.
1. "Why pray for anyone's conversion if God has chosen before the foundation of the world who will be his sons?" A person in need of conversion is "dead in trespasses and sins" (Ephesians 2:1); he is "enslaved to sin" (Romans 6:17; John 8:34); "the god of this world has blinded his mind that he might not see the light of the gospel of the glory of Christ" (II Corinthians. 4:4); his heart is hardened against God (Ephesians 4:18) so that he is hostile to God and in rebellion against God's will (Romans 8:7).
Now I would like to turn the question back to my questioner: If you insist that this man must have the power of ultimate self-determination, what is the point of praying for him? What do you want God to do for Him? You can't ask that God overcome the man's rebellion, for rebellion is precisely what the man is now choosing, so that would mean God overcame his choice and took away his power of self-determination. But how can God save this man unless he act so as to change the man's heart from hard hostility to tender trust?
Will you pray that God enlighten his mind so that he truly see the beauty of Christ and believe? If you pray this, you are in effect asking God no longer to leave the determination of the man's will in his own power. You are asking God to do something within the man's mind (or heart) so that he will surely see and believe. That is, you are conceding that the ultimate determination of the man's decision to trust Christ is God's, not merely his.
What I am saying is that it is not the doctrine of God's sovereignty which thwarts prayer for the conversion of sinners. On the contrary, it is the unbiblical notion of self-determination which would consistently put an end to all prayers for the lost. Prayer is a request that God do something. But the only thing God can do to save a lost sinner is to overcome his resistance to God. If you insist that he retain his self-determination, then you are insisting that he remain without Christ. For "no one can come to Christ unless it is given him from the Father" (John 6:65,44).
Only the person who rejects human self-determination can consistently pray for God to save the lost. My prayer for unbelievers is that God will do for them what He did for Lydia: He opened her heart so that she gave heed to what Paul said (Acts 16:14). I will pray that God, who once said, "Let there be light!", will by that same creative power "shine in their hearts to give the light of the knowledge of the glory of God in the face of Christ" (II Corinthians 4:6). I will pray that He will "take out their heart of stone and give them a heart of flesh" (Ezekiel 36:26). I will pray that they be born not of the will of the flesh nor of the will of man but of God (John 1:13). And with all my praying I will try to "be kind and to teach and correct with gentleness and patience, if perhaps God may grant them repentance and freedom from Satan's snare" (II Timothy 2:24-26).
In short, I do not ask God to sit back and wait for my neighbor to decide to change. I do not suggest to God that He keep his distance lest his beauty become irresistible and violate my neighbor's power of self-determination. No! I pray that he ravish my unbelieving neighbor with his beauty, that he unshackle the enslaved will, that he make the dead alive and that he suffer no resistance to stop him lest my neighbor perish.
2. If someone now says, "O.K., granted that a person's conversion is ultimately determined by God' I still don't see the point of your prayer. If God chose before the foundation of the world who would be converted, what function does your prayer have?" My answer is that it has a function like that of preaching: How shall the lost believe in whom they have not heard, and how shall they hear without a preacher, and how shall they preach unless they are sent (Romans 10:14f.)? Belief in Christ is a gift of God (John 6:65; II Timothy 2:25; Ephesians 2:8), but God has ordained that the means by which men believe on Jesus is through the preaching of men. It is simply naive to say that if no one spread the gospel all those predestined to be sons of God (Ephesians 1:5) would be converted anyway. The reason this is naive is because it overlooks the fact that the preaching of the gospel is just as predestined as is the believing of the gospel: Paul was set apart for his preaching ministry before he was born (Galatians 1:15), as was Jeremiah (Jeremiah 1:5). Therefore, to ask, "If we don't evangelize, will the elect be saved?" is like asking, "If there is no predestination, will the predestined be saved?" God knows those who are his and he will raise up messengers to win them. If someone refuses to be a part of that plan, because he dislikes the idea of being tampered with before he was born, then he will be the loser, not God and not the elect. "You will certainly carry out God's purpose however you act but it makes a difference to you whether you serve like Judas or like John." (Problem of Pain chapter 7, Anthology, p 910, cf. p 80)
Prayer is like preaching in that it is a human act also. It is a human act that God has ordained and which he delights in because it reflects the dependence of his creatures upon Him. He has promised to respond to prayer, and his response is just as contingent upon our prayer as our prayer is in accordance with his will. "And this is the confidence which we have before Him, that if we ask anything according to His will, He hears us" (I John 5:14). When we don't know how to pray according to God's will but desire it earnestly, "the Spirit of God intercedes for us according to the will of God" (Romans 8:27).
In other words, just as God will see to it that His Word is proclaimed as a means to saving the elect, so He will see to it that all those prayers are prayed which He has promised to respond to. I think Paul's words in Romans 15:18 would apply equally well to his preaching and his praying ministry: "I will not presume to speak of anything except what Christ has accomplished through me, resulting in the obedience of the Gentiles." Even our prayers are a gift from the one who "works in us that which is pleasing in his sight" (Hebrews 13:21). Oh, how grateful we should be that He has chosen us to be employed in this high service! How eager we should be to spend much time in prayer!