To summarize your question: Can a person who has never heard the gospel, but only has a general belief in God, be saved from his sins?
The short answer is: no. Why do I say this? Because belief in the existence of God is something all human beings clearly know, and are condemned for it. The Apostle Paul argues in his letter to the Christians at Rome:
18 For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men who suppress the truth in unrighteousness, 19 because that which is known about God is evident within them; for God made it evident to them. 20 For since the creation of the world His invisible attributes, His eternal power and divine nature, have been clearly seen, being understood through what has been made, so that they are without excuse. 21 For even though they knew God, they did not honor Him as God or give thanks, but they became futile in their speculations, and their foolish heart was darkened. 22 Professing to be wise, they became fools, 23 and exchanged the glory of the incorruptible God for an image in the form of corruptible man and of birds and four-footed animals and crawling creatures. (Romans 1:18-23, NASB).
Taking a closer look at verses 19-21, we see that knowledge about God is “evident within them.” How is this knowledge made evident? Paul answers this: “for God made it evident to them.” Someone might then ask: what is it that they know about God, and how do they possess this knowledge? Paul answers this as well: God’s invisible attributes, His eternal power and divine nature - all clearly visible by looking at the created order.
All men have this general knowledge about God and His existence, but what is the unregenerate man’s natural reaction to this clearly revealed truth? To suppress it (vs 18), not to honor God or give Him thanks (vs 21), to become futile in their speculations (vs 21), claiming to have wisdom, yet in reality becoming fools (vs 22), and worshipping created things rather than the Creator (vs 23).
Furthermore, all men have God’s moral requirements written on their hearts, and know what is good and evil (Romans 2:14-15). But even having an understanding of what is right and wrong in the sight of God is not enough to deliver one from the consequences of sin. This moral understanding accuses them, pointing toward the final Day of Judgment in which the Lord will judge people by His perfect moral standard (Romans 2:15-16).
Up to this point, we have discussed 2 ways in which God has revealed Himself: the creation itself, and also His moral requirements given to all men. Theologians call this “General Revelation” because it is given to everyone generally.
Separate and distinct from general revelation is “Special Revelation,” which may basically be understood to mean the clear revelation found in the Bible, including the gospel. Only knowledge of special revelation, and specifically of the gospel can deliver sinners from the consequences of their sins. For example, Paul says earlier in his letter to the Romans:
16 For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek. 17 For in it the righteousness of God is revealed from faith to faith; as it is written, “But the righteous man shall live by faith.” (Romans 1:16-17, NASB).
Let me ask the question: what is the power of God for salvation to everyone who believes? Is it a general knowledge of God that has been revealed to all men? On the contrary; Paul is explicit, in that it is the gospel that contains the power of God for salvation. He continues in the next verse: “For in it the righteousness of God is revealed.” The righteousness of God is revealed in the gospel of Jesus Christ, and not by another means.
Our Lord put it this way:
6 Jesus said to him, “I am the way, and the truth, and the life; no one comes to the Father but through Me. (John 14:6, NASB).
The Lord Jesus was making a claim to exclusivity here. If one wants a right relationship with the Father, one must come through Jesus Christ. He is not one of many ways, not one of many truths, not one of many means to life. He is the exclusive way, the exclusive truth, and the exclusive means to life.
In one of his first sermons, Peter said this about Christ:
12 And there is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved.” (Acts 4:12, NASB).
Getting back to Paul’s letter to the Romans, he continues his argument in chapter 3, one of the great discussions about how sinful men may be justified in the sight of God:
21 But now apart from the Law the righteousness of God has been manifested, being witnessed by the Law and the Prophets, 22 even the righteousness of God through faith in Jesus Christ for all those who believe; for there is no distinction; 23 for all have sinned and fall short of the glory of God, 24 being justified as a gift by His grace through the redemption which is in Christ Jesus; 25 whom God displayed publicly as a propitiation in His blood through faith. This was to demonstrate His righteousness, because in the forbearance of God He passed over the sins previously committed; 26 for the demonstration, I say, of His righteousness at the present time, so that He would be just and the justifier of the one who has faith in Jesus. (Romans 3:21-26, NASB).
While I won’t have time to fully interact with this remarkable text (one of my favorites, I might add), there is one point I wish to draw from it: Paul argues that the righteousness of God is made known “through faith in Jesus Christ for all those who believe.” Therefore, it is with the strongest convictions that Christians can rightly say that only those who have faith in Christ are justified in the sight of God. The righteousness of God is revealed through faith in Christ … not in some bland, generic, non-specific belief in the existence of God.
This brings me to your next question: what about the one who has never heard the gospel? Can such a one be saved apart from hearing the gospel?
I believe that the clear answer from Scripture is: no. Salvation is found only in Jesus Christ. One must not merely possess the general revelation of God’s existence and divine attributes. One must also have an understanding of the special revelation as revealed in the Bible, particularly of the gospel of Jesus Christ. This has been demonstrated in the above texts of Scripture.
I find that using exaggerated hypothetical examples can sometimes be helpful to make a point, so in the scenario where someone is born alone, lives alone, and dies alone, stranded on a desert island, and has never heard the gospel - what will become of this person? Unfortunately, this hypothetical person was clearly not one of God’s elect because he did not hear and believe in the gospel. I should add that the only reason we know with certainty that this desert island dweller was not chosen by God for salvation, is because it is a hypothetical example whereby we know he has never heard the gospel, and therefore, never believed the gospel.
Because we do not possess a knowledge of those whom God has predestined to save from their sins, we preach the gospel to all men everywhere. It is our desire to preach to everyone, for the sake of God’s elect (2 Timothy 2:10), recognizing that we are the means by which the gospel is preached (1 Corinthians 1:21), which alone has the power to save sinners. The Great Commission found in Matthew 28:18-20 reminds us of the principle that we are to preach the gospel to all the nations, and to all people’s everywhere - even those who might be stranded on a desert island. And we do this knowing that God will save whom He has decided to save, but we are to be faithful witnesses to the ends of the earth, as commanded by God.
Having said all of this, I would like to spend a few moments to respond to your friend’s argument: Since Jesus is God, if someone has a general knowledge of God and a belief in this general God, can they be saved? For many of the reasons mentioned above, I would say: no. One must have knowledge that exceeds the general revelation made known to all men; one must have knowledge of the gospel. This means that one must have a basic knowledge of the Trinity - even if they are not able to exhaustively define the Trinity, they need to know there is only one true God, and that the Father, the Son, and the Holy Spirit are God - yet distinct Persons from one another.
We have covered a lot of ground in this email, and my hope and prayer is that this has been beneficial for you. Please let me know if you have further questions or concerns, or would like to talk about any of this further. It would be my privilege to do so.
Because of the finished work of Christ,
Rusty