On a recent post Kevin DeYoung addressed the dilemma that so many Calvinists, or even Calvinist critics have been struggling with, "If God has predestined his elect to be saved no matter what, then why does it matter if I share the gospel? They're going to get saved one way or another, right?"
He comments that even though at first glance this line of thinking seems logical, it's not biblical. Here's a little bit of the post but you can find it in its entirety by clicking the title of this post.
God can work without means, or contrary to means, but he usually works through means; which means…he uses us. If you get in a bad car accident, God could save you by angelic intervention, or he could save you by a miracle when you should have been dead, but he can also save you with your seat belt. God uses means to achieve his purposes, and evangelism (and prayer for that matter) is one of those means.
God ordained proclamation to accomplish his purposes. We share the gospel out of joyful obedience, and in hope that the God who appoints the end also ordains the means. Someone asked Spurgeon once, “Why do you preach if you believe in election?” His response: “Because the elect don’t have yellow stripes down their back.” In other words, we don’t whom the elect are, so we declare the gospel without discrimination, trusting that the sheep will recognize the master’s voice.
Actually, the only evangelistic hope we really have in a hard-hearted, disobedient world is that the Lord has elect sheep out there, wandering though they now may be, who will hear his voice when we open our mouths to speak on behalf of the Good Shepherd.