First, there is common ground between Christians and unbelievers of all kinds in that we have all been created in the image of God. It is that dynamic that allows us to converse with one another in an intelligent way. Beyond that, all persons have a knowledge of God that they have suppressed (Rom. 1:18f). It is true that the image of God in man has been marred and unbelievers cannot interpret spiritual things properly and therefore cannot be convinced of the truth through human reason alone as their minds are darkened, and it is also true that unbelievers one hundred percent of the time actively suppress the knowledge of God they have and cannot and will not acknowledge the true and living God in a saving sense in and of themselves. Nevertheless, common ground does exist that provides the basis for dialogue.
Second, God has purposed to save guilty, hostile rebels from sin, Satan, death, and His wrath. He has a purpose of grace to gather all things together in Christ including redeemed sinners adopted into the family of God to the praise of His glory (Eph. 1:3-14). If God has purposed to do something, who can stop Him? As the prophet declared without hesitation, “For the LORD of hosts has purposed, and who will annul it? His hand is stretched out, and who will turn it back? (Isa. 14:27).” God’s purpose cannot be thwarted by anything including rampant pluralism.
Third, God has chosen the means by which rebels will be saved: the gospel of Jesus Christ. Don’t overlook the massive power in Paul’s bold affirmation, “For I am not ashamed of the gospel of Christ, for it is the power of God to salvation for everyone who believes (Rom. 1:16a).” Unbelievers reject the gospel but it is that same gospel that is God’s power unto salvation.
Fourth, we do not speak alone. There is a second voice that speaks when we speak: the voice of the Holy Spirit of the Living God. It is true that “the natural man does not receive the things of the Spirit of God, for they are foolishness to him; nor can he know them, because they are spiritually discerned (1 Cor. 2:14).” But bound up in that verse is the same truth Christ uttered in a different context and way. In other words, it is also true that, “You must be born again. The wind blows where it wishes, and you hear the sound of it, but cannot tell where it comes from and where it goes. So is everyone who is born of the Spirit (Jn. 3:7-8).” The Holy Spirit is at work applying the gospel to the hearts of men, women, boys, and girls unto salvation.