I'm going to jump in here because I think this is an issue with huge implications on one's spiritual walk and how they see the gospel.
First, I don't think we can become a Christian or "get saved" and then live any way we want. As Paul said, "How can we who died to sin still live in it?" (Rom. 6:2).
Second, I don't think we can lose our salvation. I believe part of the promise of the new covenant that we have with Christ is that God will keep us. He will preserve us and, thus, we will
persevere.
What's my basis for saying this?
Jeremiah 32:40 I will make with them an everlasting covenant, that I will not turn away from doing good to them. And I will put the fear of me in their hearts, that they may not turn from me.
Jeremiah 32:40 seems very clear, we are kept by the providence of God. The promise in making the new covenant is that God will change our hearts, such that we will not turn from him. But I think Romans 5:8-10 gives us an even stronger argument than Jeremiah:
Romans 5:8–10 but God shows his love for us in that while we were still sinners, Christ died for us. Since, therefore, we have now been justified by his blood, much more shall we be saved by him from the wrath of God. For if while we were enemies we were reconciled to God by the death of his Son, much more, now that we are reconciled, shall we be saved by his life.
Paul is using a type of argument here that has a technical name in logic. It's called the
a fortiori and it argues from the lesser to the greater. In this case, since we have obtained
x, then we can be even more certain in obtaining
y. Paul looks at something that is true of believers now (justification, reconciliation) and argues that because of this, our obtaining a future state (future salvation) is even more certain.
But if we can lose our salvation, I don't see how anyone can make sense out of Paul's argument. For if we can lose our salvation, then we cannot be certain that, having been reconciled to God presently, we may not lose that reconciliation and fail to be "saved by [Christ's] life." Thus, Paul's argument would be obviously false.
There are many other verses that I think I could marshal to support this view. And I'm well aware of all the verses that people utilize to argue that we can lose our salvation. I think I have good responses to those arguments (and personally I've never seen good responses to the sort of argument I've just given above), and if necessary I may come back and give those responses (if I have time).
However, I'd like to add that I think the idea that we need to do good works in order to keep our salvation can be damaging in one of two ways. Before I mention what those are, someone might object to the idea that we "do good works" in order to keep salvation. For instance, my brother believes that we can lose our salvation, but he objects to me casting it in these terms. He says what we need to keep is faith. However, ask him what faith looks like. He will take you to James where he talks about
works. Ask him if one can have faith and live in adultery or live any life characterized by sin. He will say no. So, ultimately
faith ends up meaning
faithfulness. Faithfulness in what? In being a good person (=doing good works). So either way you try to spin, it will ultimately boil down to doing enough good works (or being a good enough person) to keep your salvation. So no sense trying to sugarcoat it and say we need to keep faith when ultimately this ends up being the same as doing good works and being a good enough person.
Now getting back to the point, this can be damaging in one of two ways. Either a person may fall into despair, recognizing how sinful they are and that they will never keep their salvation if it is up to them, or a person may become prideful and blind to sin, thinking they are such a good person when in fact they aren't. Or there is a third route: a person may simply hold to the belief in a way that isn't very meaningful to them. They may believe that we can lose our salvation simply as theoretical matter, never letting it connect to their life. This is how many people hold to the doctrine that we can lose our salvation, but this isn't too surprising since this is how many people hold to god-belief anyway.
While I think each response is misguided, since it stems from a misguided belief, the first response (despair) is the proper one (in so far as one can properly respond to a misguided belief, short of abandoning that belief). For if we can lose our salvation then we truly cannot keep it because we truly are wretched sinners. And so the person who puts his hope in himself to keep his salvation (and make no mistake, anyone who believes we can lose our salvation must put their hope in themselves) will find themselves in a state of despair and without hope. The second and third responses are very dangerous because both involve the person being self-deceived to not recognize the gravity of the situation.
