Salvation is by grace through faith. That is a foundational truth. But it is usually understood to mean that nothing you do contributes to salvation. With this, a pervasive passivity enters the scene. You will even be told by some that your very faith in Christ as the sacrifice for your sins is not something you do, but something God just produces in you (or not). It is not just that grace is "unmerited favor," but that it is something exterior to you—an event involving God in heaven, a transfer of merit from Christ to your "account."
Now when that is done it is done. "Salvation" is complete. On some Soteriologies you have to service the account in various ways if you are going to make it in—faithfulness to the sacraments, for example, or periodic repentance and efforts to do better, perhaps, or even re-baptism—but only in cases few to none is there an insistence that you have to be significantly transformed into Christlikeness to "get in."
In one tradition it is said that gratitude for forgiveness will in fact make you adhere to Christ in such a way that transformation and obedience will follow. That has happened, and perhaps still happens in some cases. But if you simply observe the groups that propose this, you will see, I think, that the rate of radical transformation in them is quite low, and usually no higher than in groups which do not hold their view.
The conclusion I draw from all of this is that a view which takes salvation to be the same thing as justification—forgiveness of sins, and assurance of heaven based upon it—cannot come to see spiritual formation as a natural part of salvation. The result of that will be the routine omission of spiritual formation unto Christlikeness as a serious objective of individuals and groups who hold a mere "justification" view of salvation.
Further, it seems to me, adherence to this view of salvation is what accounts for the transformation of Evangelical Christianity into a version of nominal Christianity over the course of the 20th Century, even though, historically, Evangelicalism has strongly opposed nominal Christianity.
But is there a recognizably Christian view of salvation—one prominent in scripture and history—that does have spiritual formation as a natural part or outgrowth of "salvation," understood to be an identifiable status (sometimes, at least, associated with a specific event)? You will perhaps not be surprised to hear me say that there is such a view, and that it comes in the form of the theological concept of regeneration.
This is the event of a new type of life entering into the individual human being. The kind of life that the human being has on its own—its "natural" life, so to speak—is a kind of "death" compared to the type of life that begins to move in us at "re-generation." Once this is mentioned, I believe the person familiar with the New Testament writings will recognize the passage from "death" to "life" as a constant biblical theme, where "life" is a real and powerful presence in the regenerate individual. (Eph. 3:20; 2 Tim. 2:1)
John the Apostle states as a sure indication that we have "passed out of death into life, we love the brethren. He who does not love abides in death." And also: "He who has the Son has life." (1 John 5:11-12) "Life" is perhaps John’s favorite term for what happens when one comes to Christ. It is the entire point of "the birth from above" as discussed in John 3—a passage that is desecrated by the usual reading of it as focused upon forgiveness of sins. There the "life" is associated with seeing and entering the kingdom of God. "Birth" and "life" of course go together. Paul describes the action of God in saving us: "For He delivered us from the domain of darkness, and transferred us to the kingdom of His beloved Son." (Col. 1:13)
To enter the kingdom is to have the life "from above." That life is the principle of kingdom inclusion. It is otherwise described by Paul as sharing in the resurrection life of Jesus himself. "You have died and your life is hidden with Christ in God." (Col. 3:3) Again: "You were dead in your trespasses and sins…. But God…, even when we were dead in our transgressions, made us alive together with Christ (by grace you have been saved), and raised us up with Him, and positioned us with Him in the heavenlies in Christ Jesus." (Eph. 2:1-6) That is what the birth "from above" does. Simple inductive study of the New Testament will, I believe, convince anyone that the primary way of understanding salvation according to it is in terms of a divine life that enters the human being as a gift of God.
There is then a new psychological reality that is God acting in us and with us. Eternal life is said by Jesus to be knowledge. Knowledge in biblical language is an interactive relationship, and in this case with "Thee, the only true God, and Jesus Christ whom Thou hast sent." (John 17:3) Eternal life in the individual does not begin after death, but at the point where God touches the individual with redeeming grace and draws them into a life interactive with Himself and His kingdom.
A new, non-human activity becomes a part of our life. Our life is now interwoven with His and His (amazing grace indeed!) with ours. Speaking thus we must make it clear that we are not just "talking something up," but referring to the concrete reality of regenerate existence.
Segments taken from a lecture presented at the 2009 Wheaton Theology Conference. http://www.dwillard.org. Used by permission.