You are explaining the gospel to an individual and he says, “I just can’t believe there is only one of way to heaven.” Perhaps you are frozen in your tracks as you think, “what do I do now?”
I usually say something like this, although there are no “silver bullets” for questions like these:
God is not obligated to make a way of salvation for those who have shattered his laws and violated his standards in rebellion against him. However, God in his mercy and grace has made a way of salvation for those very people; He did not have to do this to begin with. Further, He could have made a 2nd or 3rd way of salvation, but man in his rebellion would have sought a 4th or 5th or 78th. The problem, then, is not with God, nor with His way of salvation; the problem is ours. We will not come to God on His terms; we will not follow His way.*
*I first heard this concept on a Ravi Zacharias podcast.