All men do not hear a clear presentation of the gospel. That is the fault of God's people not taking the gospel to all the world. Paul told the Corinthians, "Awake to righteousness, and sin not; for some have not the knowledge of God: I speak this to your shame" (1 Corinthians 15:34).
However, all men are responsible for their rejection of God. As the Bible says, they are "without excuse" (Romans 1:20). How can this be?
Although all men do not hear a clear presentation of the gospel, all men do have a calling from God that they either receive or reject. Consider these verses:
Psalm 98:2 The LORD hath made known his salvation: his righteousness hath he openly shewed in the sight of the heathen.
John 1:9 That was the true Light, which lighteth every man that cometh into the world.
John 12:32 And I, if I be lifted up from the earth, will draw all men unto me.
Romans 1:19 Because that which may be known of God is manifest in them; for God hath shewed it unto them.
Titus 2:11 For the grace of God that bringeth salvation hath appeared to all men,
These verses teach that God deals personally with every man who comes into the world and draws him to Himself. He may do it through creation or through personal circumstances, but in some way He shows Himself to be real to that person. At some point in time, each person comes to a crisis of heart where the light he has must either be accepted or rejected.
Unfortunately, when this light comes, most men reject it. Yet, there are some who receive the light given to them and seek to know more about the true God. These seekers know there must be more to eternal things than what is taught to them by their religious leaders. To those who seek the Lord on the basis of the minimal light they have, God gives this promise: "And ye shall seek me, and find me, when ye shall search for me with all your heart" (Jeremiah 29:13). To those who seek with all their hearts, God will send a messenger with the truth of the gospel whereby they may be saved.
We have an example of this in the salvation of Cornelius in Acts ten. He feared God and prayed to Him (Acts 10:2), but he still needed to hear the gospel of Jesus Christ so that he could be saved (Acts 11:14). Because he sought the Lord with the light he had, God sent him more light.
There are multiplied examples of this in the history of missions. A missionary will be led by the Lord to go to an out-of-the-way place to present the gospel. Then, some old man or woman who gets saved will give the testimony that this is what they have been looking for their entire life. They sought and God sent.
Therefore, no man is without excuse--even if he has never clearly heard the gospel. However, the Bible clearly demonstrates that many who will not seek on their own would be saved if we would go and tell them. This sword has two edges. They are responsible for the light God gives them and there is no excuse. However, we are responsible for telling them and it is a shame to the Christians of this world that many do not have the knowledge of our Lord and Saviour Jesus Christ. We have blood on our hands.