I consider myself to be a Calvinist in most respects, though I am admittedly not well-studied in all that being a Calvinist entails. The one thing I do believe is that salvation comes by nothing which we can ever do on our own, and therefor it is only those God has predestined for salvation who can ever be saved. However, that is not the point of this thread.
My question is, how do you reconcile this belief with a need for missionaries, or even a need to make an altar call on Sunday morning? I do believe that missions is important (as we have been mandated by Christ to do so), but I find it difficult to put into words why it is important in light of predestination. Or is it important in your mind?
There're two other things going on here, none of which is directly impacted by the regeneration of people by the Spirit of God.
First, there's a point Jesus made about people who are born(e) by the Spirit of God. "
The Spirit [aka wind] blows where it wishes, and you hear its sound, but you do not know where it comes from or where it goes. So it is with everyone who is born of the Spirit." John 3:8 Jesus is saying that you and I are carried along by the Spirit wherever He wants to take us.
And what's our purpose?
Well, we're not
making people into the reborn. We don't do the making. We're trailing along after the Spirit to try to discover our brothers in Christ. They're family.
If I knew members of my family were lost, I'd want to strike out to find them. If they're unaware of their family background, I'd want to bring the announcement that makes them aware. The Spirit brings these people to birth, to see the spiritual in the world. We're here to wake them up to educate them in the awareness of what that spiritual world really looks like beyond their wide-eyed infant eyes might think is real, but is more tossing them back & forth.
And that stretches into some really fundamental parts of reality, like depending on Jesus, understanding His Crucifixion and Resurrection, and embracing the Gospel. When people do that, we're allowed to consider them part of the family, sons of God. When they don't, we draw from that that they haven't seen, and either aren't awake yet -- or aren't alive.
How then will they call on him in whom they have not believed? And how are they to believe in him of whom they have never heard? And how are they to hear without someone preaching? And how are they to preach unless they are sent? As it is written, "How beautiful are the feet of those who preach the good news!" But they have not all obeyed the gospel. For Isaiah says, "Lord, who has believed what he has heard from us?" So faith comes from hearing, and hearing through the word of Christ.