Apparently many sincere people are trusting in their sincerity for salvation. But is sincerity enough? Jesus said, "I am the way, the truth, and the life: no man cometh unto the Father, but by me" John 14: 6. Now what could this possibly mean if sincerity alone is sufficient? If there is no other way to salvation than through Christ, as he clearly stated here, then sincerity alone will not do, will it?
One of the classical examples of a man who was unquestionably sincere, and yet lost, out of Christ, and even an arch enemy of the early church, is that of Saul of Tarsus. Saul had even participated in the murder of the first Christian martyr, Stephen (Acts 7: 58). He "made havoc of the church ... and haling (dragging) men and women committed them to prison" Acts 8: 3. It is even reported further that "Saul, yet breathing out threatenings and slaughter against the disciples of the Lord, went unto the high priest, and desiring of him letters to Damascus to the synagogues, that if he found any of this way, whether men or women, he might bring them bound unto Jerusalem" Acts 9: 1,2. So here is a man who is religious about persecuting the way of Christ, believing Jesus to be an imposter. Yet, though misguided, he said, "I have lived in all good conscience before God until this day" Acts 23: 1. He had been sincere, but that sincerity wasn't enough, because you see, sin is not just a matter of violating your conscience; it is a matter of violating the will of God. John was speaking of this in I John, Chapter 3, verse 4, when he said, "Sin is the transgression of the law".
In course of time a Christian named Ananias informed Saul, "Why tarriest thou? Arise, and be baptized, and wash away thy sins, calling on the name of the Lord" Acts 22: 16. Yet Saul's story ends happily because when he learned the error of his way, he was sincere enough to turn from his sins to Christ and he went on to become the great Apostle Paul.
Let's look at another New Testament example. In Acts Chapter 2, you read that there were dwelling at Jerusalem, Jews, devout men, out of every nation under heaven (verse 5). Yet, as Peter preached to these sincere people, he accused them with these words: "Him (that is Jesus Christ) ... you have taken, and by wicked hands have crucified and slain" (verse 23). Although they were devout, they had participated in the crucifixion of the Lord. On learning of their sin, they were (as the Bible says) "pricked in their heart, and said unto Peter and the rest of the apostles, 'Men and brethren, what shall we do?"' (verse 37). They now realized that they were guilty before the Lord God. And as they were searching for a cleansing from this guilt, Peter said to them, "Repent and be baptized every one of you in the name of Jesus Christ for the remission of sins ... " Acts 2: 38.
The role of sincerity is to enable a person to be fair and honest with the truth! Sincerity alone does not determine truth, scientifically, and medically, legally, or religiously. You can see then, what Jesus was getting at when he said, "Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven" Matthew 7:21.