So when someone tells us they know a Catholic who is a born-again Christian, we have to ask, how do you know? Since no one can see a person’s heart, it is impossible to know with absolute certainty "who" is a Christian. However we can know with certainty "what" is a Christian. From the Bible we know a Christian is one who has been called by God according to His purpose and grace to believe on the One He sent (John 6:29; 2 Tim. 1:9). A Christian knows God’s word is true through the ministry of the indwelling Holy Spirit (1 Cor. 2:12), He has the ability to discern truth from error and has a teachable spirit (1 John 4:6). A Christian is one who has received eternal life, the complete forgiveness of sins and a right standing before God by forsaking all efforts to save himself and by transferring his trust to the Lord Jesus Christ (Eph. 2:8-9, Col. 2:13). By abiding in God’s word, the Christian is liberated from man’s traditions and legalistic bondage (John 8:31-32). A Christian is one who is motivated to obey God’s commands by His love for God, not to merit salvation (1 John 5:13). He endeavors to live according to God’s will, to do the things pleasing to God and to avoid the things that God hates (Titus 2:11-14).

A true understanding of the Gospel is necessary to trust God’s only provision for the salvation of sinners. Often, the truth must be contrasted against the errors of religious indoctrination for the Gospel to be clearly understood. Biblical terms must be shared and defined in order to expose man’s traditions and philosophies that oppose the Gospel. Only by asking questions can we know if a Roman Catholic has a true understanding of the glorious Gospel of grace. Following are some key questions to ask professing Christians.

Did you know that you must be born again to see the Kingdom of God? When and how were you born again? What were the events that led to your conversion? Catholics tend to interpret their conversion in light of their indoctrination. They usually refer to their baptism as their conversion and consuming the Eucharist as the means to receive Christ. Many Catholics are reluctant to talk about these things which may be an indication that there has been no conversion. Those who have experienced the second birth will want to sing the praises of the one who called them out of darkness into His glorious light (1 Pet. 2:9). Giving details of a conversion brings great joy to other Christians (Acts 15:3).

What were you converted from and to? Were you converted from a religion to a relationship with God? Has God converted you from a slave to sin to His adopted son and heir? A Christian will be able to say what John Newton said, "I am not [yet] what I ought to be, but I am not what I once used to be, and by the grace of God I am what I am."

Is faith necessary to be saved? If it is, how do you explain the Catholic teaching that infants are saved, not by faith, but by water baptism? Has the object of your faith ever changed? On what do you base your salvation? Is the Lord Jesus Christ the object of your faith and obedience or do you still trust and submit to the teachings and traditions of the Catholic Church? Is it possible to believe two opposing doctrines at the same time? Do you believe there is only one Gospel of salvation? What is the Gospel? How can you discern which Gospel has the power to save sinners and which gospel condemns those who preach it? (Gal. 1:6-9). Are you relying on what Christ has done (grace) or what you are doing (works) for your salvation? In whose righteousness are you trusting for entrance into heaven?

If you were to leave the Catholic Church would you still be saved? Do you know that God’s righteous justice demands death as punishment for even the smallest of sins? (Rom. 6:23). Even if you keep the whole law and yet stumble at just one point, you are guilty of breaking the whole law? (James 2:10). Catholics are taught that only certain types of sins are deadly. Have you been completely forgiven from the guilt and punishment of all your sins, past and future, mortal and venial? Or do you still believe Purgatory is necessary to purge away the sins that were not purified by the blood of Jesus? What about indulgences? Do you believe they are necessary for the remission of temporal punishment for sin? Catholics are taught by doing penance, the guilt of certain sins is forgiven but the punishment still remains to be paid by indulgences and/or suffering in purgatory.

Do you believe Jesus bore your sins and was condemned in your place to bring you to God? Do you believe He canceled your infinite sin debt and removed the entire curse of the law as the Bible promises? What do you believe about the Mass? Can Catholic priests really offer sacrifices for sins after Jesus offered Himself once for all sin for all time? Can you show me in the New Testament where the early church followed this practice? Why does the Catholic Church continue the one-time event that Jesus said "is finished"? (John 19:31). The Bible teaches that the one offering of Jesus Christ has made perfect forever those who are sanctified (Heb. 10:14). The offering was sufficient and is never to be offered again (Heb. 10:18).

These questions will not only determine if a Catholic has truly been converted to Christ, they will also help a new convert grow in grace and truth. The questions can also be used as a scalpel to cut away the traditions of men that often hinder a believer’s spiritual growth. Please note that all these questions are focused on the Lord Jesus Christ and what He did to reconcile condemned sinners to God. Avoid asking questions unrelated to the core issue, "What must I do to be saved?"

We do people a grave disservice if we encourage them in a spurious faith. If their faith is not in Christ alone, they remain separated from God and under His wrath. If we do not lovingly confront them in their true spiritual condition, they risk the irreversible tragedy of being condemned by Jesus at the Great White Throne judgment. I cannot think of anything more horrifying than a professing Christian, coming face to face with Jesus, and hear Him say, "I never knew you; depart from Me" into the eternal lake of fire. Yet, there are many Catholics and non-Catholics who will hear these words unless they come to know and trust Jesus through His word.

Doctrinal error must be lovingly exposed and corrected using the infallible word of God. False teachings that have been craftily veiled with truth can be difficult to detect. In fact, seldom is error presented without first mixing it with truth lest it immediately be identified. Those who use doctrinal error to control and deceive the unsuspecting are outwardly covered with sheep’s clothing but inwardly are ravenous wolves. Catholics must be warned, their eternal destinies hang in the balance.