Contrary to Catholic belief, some Protestants teach that once we believe in Jesus we can be absolutely sure we’re going to heaven. They quote 1 John 5:13 as a proof text: “I write this . . . that you may know that you have eternal life.”
Does this text teach what some Protestants think?
The term “knowledge” can be used for different kinds of intellectual certainty. Sometimes, it is used to convey absolute certitude. For example, I know that 1 + 1 = 2.
But “knowledge” can also be used in a way that doesn’t imply absolute certitude. For example, I may say that I “know” I’m going to earn an A on my philosophy exam because I’ve studied hard and I’m familiar with the material. But that doesn’t mean that I have infallible knowledge (knowledge without the possibility of error), since I could very well goof up and get a B. Rather, I have a reasonable expectation.
Since the term knowledge can take the form of either absolute certitude or reasonable expectation, it’s wrong to conclude that we can have absolute assurance that we’re going to heaven just because John says that his readers can “know” they have eternal life.
So, this raises the question: How did John intend for us to understand “know” in this case?
Some Protestants will argue that it’s a knowledge that entails absolute certitude because it’s revealed that whoever believes in Jesus will not perish but have eternal life (John 3:16). Since John’s words in 1 John 5:13 are directed at those who “believe in the name of the Son of God,” it follows that their knowledge that they will attain eternal life at the end of their lives entails absolute certitude.
The problem here is that John also teaches his readers must persevere in belief until the end of their lives in order to attain eternal life, as we see in 1 John 2:5: “Whoever keeps his word, in him truly love for God is perfected. By this we may be sure that we are in him” (emphasis added).
Then, in verse 24, John writes,
Let what you heard from the beginning abide in you. If what you heard from the beginning abides in you, then you will abide in the Son and in the Father. And this is what he has promised us, eternal life (emphasis added).
John’s readers have heard from the beginning that Jesus is the Christ and they need to confess him as such (v.22). The talk of this Gospel message abiding in them refers to belief in that Gospel message. It also refers to loving our neighbor (1 John 3:11). The implication, therefore, is that continued belief in the Gospel message, and love of neighbor, is necessary to abide in the Son and in the Father. And since to abide in the Son and in the Father is to have eternal life, it follows that continued belief in the Gospel message, which works through love (Gal. 5:6), is necessary to attain eternal life.
This motif of perseverance in faith and love unto the end has its roots in the teaching of Jesus. Consider, for example, Matthew 10:22, where Jesus says, “He who perseveres unto the end will be saved.”
We know this perseverance entails continued belief in and love for Jesus and that he’s referring to eternal salvation because just a few verses later Jesus teaches that our being acknowledged before the Father (being numbered among the elect and thus having eternal life—cf. Rev. 3:5) is dependent on whether we acknowledge him before men: “So everyone who acknowledges me before men, I also will acknowledge before my Father who is in heaven; but whoever denies me before men, I also will deny before my Father who is in heaven” (vv. 32-33).
Now that we know John believes his Christian readers must persevere in faith to attain eternal life at the end of their lives, the question becomes, “How could John’s readers possibly know with absolute certitude that they would persevere in faith unto the end of their lives?”
They couldn’t know by way of philosophical demonstration, since knowing which persons God has eternally decreed to give the grace of final perseverance to is beyond the reach of reason on its own.
They couldn’t know by way of public revelation, because no inspired writing at the time John writes this letter names any of the Christians to whom John is writing as numbered among the elect. Nor does the Bible ever say believers in general will all persevere. To suggest otherwise would make passages that warn Christians about falling away from Christ unintelligible (cf. 1 Cor. 10:12— “Therefore, let anyone who thinks that he stands take heed lest he fall”).
The only other possible way that John’s readers could have had absolute certitude concerning their final perseverance is by way of private revelation, which would involve Jesus appearing to them and telling them that they would persevere. But there’s no evidence that John’s readers did have such experiences, nor is there any evidence that John knew about such experiences.
Since these are the only ways that John’s audience could possibly have absolute certitude that they would finally persevere in faith, it’s reasonable to conclude that the knowledge John speaks of in 1 John 5:13 is not the kind of knowledge that involves absolute certitude. Rather, he speaks of a knowledge that entails confident expectation.
A Protestant might object that we haven’t exhausted all the options for private revelation. Maybe John didn’t think Jesus appeared to his readers in a vision. But he would have known they received the inner testimony of the Spirit that they are children of God, for Paul writes, “It is the Spirit himself bearing witness with our spirit that we are children of God” (Rom. 8:16).
The problem here is that to be a child of God is distinct from receiving after death the inheritance of eternal life that belongs to his children. One can be a child and still forfeit his inheritance. As such, the interior witness of the Spirit that Christians are children of God doesn’t entail absolute certitude that all will persevere in faith to receive and enjoy their inheritance of eternal life at the end of their lives.
In sum, John is consistent with the entirety of Scripture, which says we as Christians have to persevere in faith to receive the reward of eternal life at the end of our lives. We showed above that none of the ways one can arrive at absolute certitude concerning perseverance in faith applies to John’s audience. Therefore, the knowledge that John says his audience can have concerning the possession of eternal life is not the kind of knowledge that involves absolute certitude. As such, a Protestant can’t appeal to 1 John 5:13 as biblical support of the idea that Christians can know with absolute certitude that they will attain heaven at the end of their lives once they become believers.
St. Paul would have fit right in with John’s readers, since he didn’t have such certain knowledge of his final salvation. He writes, “I am not aware of anything against myself, but I am not thereby acquitted [Greek, dedikaiōmai—“justify; declare righteous”]. It is the Lord who judges me” (1 Cor. 4:4).
This doesn’t mean, however, that we can’t have any knowledge. As the Catechism of the Catholic Church teaches, by virtue of the theological virtue of hope we can a “confident expectation of divine blessing and the beatific vision of God” (CCC 2090). That’s certainly a knowledge that we can rejoice in.