At the foundational level, being justified by faith alone is pretty simple. It is simply answering the question of how a sinful man, deserving of God's judgment, is made right with God. Justification by faith alone holds that men are made right before God apart from, and indeed in spite of, any meritorious works of our own. Humble faith in Christ alone is the only means of salvation. Conversely when we claim to be justified, even in part and no matter how small, by our own efforts we turn salvation into a co-operative process. Practically speaking many Christians would hold to what is called synergistic regeneration even though they would affirm the doctrine of justification by faith alone.
Paul powerfully deals with justification by faith alone in many places but nowhere more deeply and richly than in his letter to the chuch in Rome.
For by works of the law no human being will be justified in his sight, since through the law comes knowledge of sin. But now the righteousness of God has been manifested apart from the law, although the Law and the Prophets bear witness to it-- the righteousness of God through faith in Jesus Christ for all who believe. For there is no distinction: for all have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus, whom God put forward as a propitiation by his blood, to be received by faith. This was to show God's righteousness, because in his divine forbearance he had passed over former sins. It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus. Then what becomes of our boasting? It is excluded. By what kind of law? By a law of works? No, but by the law of faith. For we hold that one is justified by faith apart from works of the law. Or is God the God of Jews only? Is he not the God of Gentiles also? Yes, of Gentiles also, since God is one--who will justify the circumcised by faith and the uncircumcised through faith. Do we then overthrow the law by this faith? By no means! On the contrary, we uphold the law. (Romans 3:20-31)Men are not right with God on the basis of circumcision (or water baptism for that matter), or by observing certain laws like the sacrifice of animals for the atonement for sin (see Leviticus 16).
They are only made right with God on the basis of faith in Christ. Going to church, giving your "tithe", voting Republican. None of them have anything to do with your salvation. Faith and faith is the only basis upon which a sinner can claim to be saved.
This is where faith and grace intersect. Most Christians can repeat the generally accepted definition of grace: God's unmerited favor. That is unfortunately as far as many people get but there is so much more to it. Justification by faith alone keeps the grace in grace. As Paul's letter to the Romans continues into chapter four he makes an important contrast while extending his larger point:
What then shall we say was gained by Abraham, our forefather according to the flesh? For if Abraham was justified by works, he has something to boast about, but not before God. For what does the Scripture say? “Abraham believed God, and it was counted to him as righteousness.” Now to the one who works, his wages are not counted as a gift but as his due. And to the one who does not work but believes in him who justifies the ungodly, his faith is counted as righteousness,(Romans 4:1-5)When I get paid every other Friday, those wages are an obligation of my employer in return for the work I have done for the prior two weeks. My employer doesn't just hand out paychecks to people walking by our building but rather pays those who work. If a payday rolled around and I didn't get paid for the time I worked, I would have the legal right to go after those wages. They are owed to me based on the employment agreement between me and my employer. Grace? I have no legal claim on God's grace. I can point to nothing I have done that makes me deserving of anything other than God's wrath. God is gracious to me in spite of my sins. Grace is only truly gracious when it comes with no obligation on the part of the dispenser. God doesn't owe you grace and He doesn't owe me grace. His grace is His to sovereignly bestow as only He deems fit.
That leaves us with the question: what of good works? Are they optional or ancillary, something that is a nice add-on to our justification or something only certain Christians are called to? It certainly doesn't seem that way. Paul, James and Jesus Christ Himself seem quite concerned with how we live out our faith. There is a lot of confusion over this because on the one hand the Bible speaks so often about the necessity of good works but likewise states unequivocally that we are saved/justified by faith alone. Is this a contradiction in the Bible or are we missing the relationship between the two? I think this second part is where many Christians get tripped up. We don't know what to do with the exhortations to good works or to holiness and piety. We are so afraid of any tinge of the Roman error of works-righteousness that we freeze into inaction or become unmotivated to exhort one another to good works. This is a mistake and a serious one. We hear Hebrews 10:25 quoted to us all the time, often as a stick to "encourage" us to "go to church" but the reason we gather is important and often ignored:
And let us consider how to stir up one another to love and good works, not neglecting to meet together, as is the habit of some, but encouraging one another, and all the more as you see the Day drawing near.(Hebrews 10:24-25)The reason we gather together, at least one of the major reasons we are exhorted to not neglect the gathering of the saints, is not to listen to sermons or to "worship", i.e. singing songs, or to "partake of the sacraments". Rather it is to stir up and encourage one another to love and good works which implies that we need that encouragement! Now whether the traditional organized religion Sunday morning "worship service" accomplishes that or not is a question for another day. Suffice it to say that one of the primary reasons we gather is for born-again believers to encourage other born-again believers to love and good works. Herein lies the paradox of mixed meetings. If we are meeting in a such a way that unbelievers and believers alike are intermixed we run the risk of exhorting a non-believer to good works which can easil lead them to a false assurance of faith based on personal piety and good works, exactly what we are trying to avoid. Again, a topic for a different day but an important side-note nevertheless.
Faith and works are not an either-or proposition. They are not opposed to one another. We just need to ensure that we get the order right. The classic way of comparing a works based salvation versus a faith based salvation is to contrast Faith+Works=Salvation to Faith→Salvation→Works. In other words, saving faith leads to justification which inexorably leads to good works in response. Faith and works are inextricably linked but not equally. One flows from the other but the one cannot exist without the other. Let me try a bold and sweeping statement:
We are not saved by our works but we are not saved apart from them either.
Works are the result of justification which comes via saving faith. My favorite verse on this progression comes from the second chapter of Paul's letter to the church in Ephesus:
For we are his workmanship, created in Christ Jesus for good works, which God prepared beforehand, that we should walk in them. (Eph 2:10)What is especially pertinent in this passage is that it follows Paul's bold declaration of the Gospel of salvation by grace alone through faith alone in Christ alone, dealing with deep theology like election and monergistic regeneration. Paul doesn't stop with "by grace you have been saved through faith" but continues on from the question of "what" to "what now". God did not save us just to save us from hell. He predestined us for adoption but He also prepared works of mercy beforehand for us to walk in. Not only does He prepare the way for our salvation but also the opportunities for service that follow our justification. If God went through the process of preparing these good works, do you think maybe they are important?
So in summary, justification, our legal standing before God as justified with our sins forgiven, comes only through faith. We add nothing to it. We are not partners in it. We don't cooperate in any way. It is all of grace. As a result of this justitication and the changed heart that is regenerated by God, our outlook changes such that we will seek ways to serve God by serving, loving and witnessing to our neighbors. This is not a natural event and that is why we are exhorted to meet as the church to encourage one another.
There is nothing new here and this is merely my clumsy attempt to work through a topic that has been written about by the greatest theologians of the church for centuries. I could point you to a number of far better treatments of this topic but it is helpful to me to work through it on my own from time to time. Hopefully it is somewhat helpful or at least gets you thinking about this most precious and crucial of truths. We need to dig beyond the surface on these doctrines. Saying we are justified by faith alone is one thing but to get deeper into the doctrine, working through it and examining the implications of it, should give you a far greater appreciation of how marvelous this truth really is. When we see ourselves standing before the King with no righteousness of our own, with no claim on His favor other than saving faith in the Savior, that is when we will be able to truly sing Amazing Grace. Then we will see how gracious, precious and all-sufficient Jesus Christ truly is. There is nothing more amazing to me than to realize that He saved a wretch like me, the least likely person I have ever met and to know that He saved me in spite of and not because of whatever merit I thought I was bringing to the table. Justification by faith alone is not a theoogical "get out of hell" card but rather is the is the bedrock of the Gospel message and while it is a doctrine that we need to spend more time studying it is also a doctrine that must spur us to action: proclaiming the Gospel, loving our neighbor, visiting the widow and orphan, sharing and edifying and equipping among the Body of Christ. There is no doctrine in the Bible that is more active, more dynamic and more pertinent to how we live as Christ's ambassadors to the world. If we turn it into merely a cold point of theological correctness we will lose how truly amazing and impactful this doctrine is.