First John, Faith and Works, and Falling Away
This is most assuredly not a “faith alone” theology.
An anti-Catholic apologist asked if Catholics could be the “blessed man” in this passage:
Romans 4:7-8 (RSV) “Blessed are those whose iniquities are forgiven, and whose sins are covered;  blessed is the man against whom the Lord will not reckon his sin.”
Yes, indeed: any other regenerated Catholic believer, not mired in mortal sin (see 1 Jn 5:16-17), is the “blessed man” here.
We can, however, lose this blessedness by means of our rebellious free will, and so those familiar with all the relevant biblical teaching on possible apostasy and the moral assurance of salvation (as opposed to some imaginary absolute assurance), agree with the Bible writers that we are in Christ and will be saved.
We’ll be saved provided that we don’t “turn back again to the weak and beggarly elemental spirits” (Gal 4:9), or “submit again to a yoke of slavery” leading to our being “severed from Christ” and “fallen away from grace” (Gal 5:1, 4), and “provided that” we “continue in the faith, stable and steadfast, not shifting from the hope of the gospel” (Col 1:23), and do not (according to what “the Spirit expressly says”) “depart from the faith by giving heed to deceitful spirits and doctrines of demons” (1 Tim 4:1), and if we have not “strayed after Satan” (1 Tim 5:15).
The apostle Paul made it clear that he himself (as in 1 Cor 9:27) had “not... already obtained” this salvation, and that he had to “press on” to make that happen (Phil 3:12); he would be saved unless “after preaching to others I myself should be disqualified” (1 Cor 9:27). He also wrote that we will be “children of God” and “fellow heirs with Christ, provided we suffer with him in order that we may also be glorified with him” (Rom 8:16-17).
The writer of Hebrews is even more crystal clear and explicit. We will be saved by God’s grace unless “there be in any of you an evil, unbelieving heart, leading you to fall away from the living God” (3:12), or if it so happens that we are “hardened by the deceitfulness of sin” (3:13), and “if only we hold our first confidence firm to the end” (3:14). Is it clear enough yet? The same inspired writer of God’s infallible revelation informs us that “it is impossible to restore again to repentance those who have once been enlightened, who have tasted the heavenly gift, and have become partakers of the Holy Spirit, and have tasted the goodness of the word of God, and the powers of the age to come, if they then commit apostasy” (6:4-6).
St. Peter continues the same sort of thought on apostasy:
2 Peter 2:15, 20-21 Forsaking the right way they have gone astray; they have followed the way of Balaam, . . . For if, after they have escaped the defilements of the world through the knowledge of our Lord and Saviour Jesus Christ, they are again entangled in them and overpowered, the last state has become worse for them than the first. For it would have been better for them never to have known the way of righteousness than after knowing it to turn back from the holy commandment delivered to them.
Lastly, I would like to examine another portion of Scripture that doesn’t fit at all into the general Calvinist / eternal security / fundamentalist mold. In those views, it’s a very simple affair: you are forgiven once and for all with a sinner’s prayer or some other outward form of committing oneself to Christ (an adult baptism or whatever). That’s it. There is no more need for forgiveness because God imputes justification to such a believer, and saves him or her once-and-for-all in that one-time event.
The problem is that 1 John (among many other passages) completely contradicts this scenario. St. John repeatedly and undeniably teaches that we must exhibit this moral assurance of salvation and being in Christ by good works (the two are hand-in-hand; two blades of a pair of scissors, or two sides of the same coin, just as they also are in James). This is most assuredly not a “faith alone” theology:
1 John 1:7 but if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus his Son cleanses us from all sin.
1 John 2:3-6 And by this we may be sure that we know him, if we keep his commandments. He who says “I know him” but disobeys his commandments is a liar, and the truth is not in him;  but whoever keeps his word, in him truly love for God is perfected. By this we may be sure that we are in him:  he who says he abides in him ought to walk in the same way in which he walked. (cf. 3:22-23)
1 John 2:29 If you know that he is righteous, you may be sure that every one who does right is born of him.
1 John 3:3 And every one who thus hopes in him purifies himself as he is pure.
1 John 3:7 Little children, let no one deceive you. He who does right is righteous, as he is righteous.
1 John 3:10 By this it may be seen who are the children of God, and who are the children of the devil: whoever does not do right is not of God, nor he who does not love his brother.
1 John 3:24 All who keep his commandments abide in him, and he in them. And by this we know that he abides in us, by the Spirit which he has given us. (cf. 5:2-3)
1 John 4:8 He who does not love does not know God; for God is love. (cf. 4:11-12, 16, 19-21)
1 John 4:20 . . . he who does not love his brother whom he has seen, cannot love God whom he has not seen.