The "fallen from grace" language is interesting. Are we to think of a different kind of "grace," or a different kind of "falling away," since we are confident that it doesn't mean losing your salvation?
That's a great question, Andrew. I think that you are perceptive to conclude that Paul cannot be speaking of an individual at one time having salvation, and then later losing it and becoming "unsaved."
When the Bible speaks about individual salvation, it presumes that conversion is something far more profound than an individual simply "making a decision" for Christ, and then later changing his mind later and undoing it all.
No, conversion is a renewal of the inner-man that begins when he is regenerated (literally: made alive again), granted new life in Christ, crosses over from death to life, receives the Holy Spirit (Ephesians 1:13-14), and is spiritually remade by grace as a new creation (2 Corinthians 5:17). Conversion, then is a complete transformation of a man that cannot be lost, stolen, or taken away (Romans 8:28-30; 37-39).
So, as with most difficult passages, context is key for Galatians 5:4.
In the Galatian letter, Paul is concerned that the church at large has been infiltrated with another "gospel" (1:6) that teaches salvation is to be obtained through other means (or in addition to) faith alone in Christ. Specifically, the Galatian church had been infiltrated by a heretical sect or leader (see 1:7; 5:12; 5:7-10). It appears that the inroads made by this false teaching, which apparently placed undue emphasis on circumcision, is putting the entire congregation in jeopardy.
This explains Paul's outrage in 1:6-9. He even calls them fools collectively (3:1)! (Note: Pastors, don't try this at home!) By the time we get to 5:4 (the text in question), Paul is ready to use even more shocking language yet to describe the precipitous danger of turning as a congregation to the slavery of the Law, under which no man is justified (Romans 3:20).
The "falling away" then, would seem to me to be a collective doctrinal failure as a Gospel-preaching church. The Galatians are at risk of becoming a cult, or sect, of true Apostolic Christianity. The grammatical use of the plural "you" in 5:4 makes me think that Paul is warning them as a whole church here, not as individuals whom he fears may get "unsaved."
"Grace" then would seem to me to refer here, not as shorthand for any one person's individual salvation, (although I grant that it is sometimes used that way) but rather the broader "grace" of being a community of believers in covenant with the gracious Christ of the Gospel. By becoming heretical, the Galatians are at risk of losing their position as a light and a witness in the world for the saving Gospel: by faith alone, in Christ alone.
Thanks for the question!
--Matthew Everhard is the senior pastor of Faith Evangelical Presbyterian Church in Brooksville, Florida.