A friend of mine has a buddy who seems to have fallen away from Christ. This sad event has raised the question for her: can someone fall away from Christ? I will quote my friend:
My question is, if someone is genuinely a Christian, can they stop being a Christian?
I know that the bible says that if someone is saved, God will hold on to them. Does this mean that if someone stops being a Christian, they were never truly a Christian in the first place?
Because of the complexity of the question, requiring more than a few sentences to answer, I am answering my friend via a blog –welcome to our conversation! Scripture’s testimony on these questions isn’t simple – perhaps because people aren’t simple! A balanced answer to these questions requires that we affirm a number of truths from scripture (I will refer to six), which can, at least at first, feel like they are in tension with one another. Here goes:
The first thing to affirm is: of course people can fall away from Christ! People do fall away from Christ! We know this from experience. And we know this from the book of Hebrews – people drift away! So, we need to be on guard.
Therefore we must pay much closer attention to what we have heard, lest we drift away from it. (Hebrews 2:1)
Second, for the theologians, this passage from Hebrews sounds like it cuts against the grain of reformed teaching, namely, the doctrine of the perseverance of the saints. This doctrine is often (and wrongly) understood to mean that if a person makes a confession of faith and evidences some fruit, they can never fall away from Christ. However this is not what the reformers meant by the doctrine. Calvin, in his Institutes, never meant that a person who confessed Christ could never un-confess Him. Rather Calvin meant that those who God has called to belong to Christ are truly called and truly held. And we are not given knowledge of precisely who Christ has truly called.
Third, in light of the blessing that Christ calls people to belong to him, we are exhorted to keep careful watch on this ‘calling’:
Therefore, brothers, be all the more diligent to make your calling and election sure. (2 Peter 1:10)
Fourth, in light of all this, in my opinion the popular phrase: ‘once a Christian, always a Christian’, is not helpful. It doesn’t reflect the whole testimony of scripture on this issue, and it can lead to complacency.
Fifth, very importantly, there are wonderful verses that promise that God will hold us. An example is found in John Chapter 10:
My sheep hear my voice, and I know them, and they follow me. 28 I give them eternal life, and they will never perish, and no one will snatch them out of my hand. 29 My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father’s hand. 30 I and the Father are one (John 10:27-30)
Or this wonderful verse, from Jude:
Jude, a servant of Jesus Christ and brother of James, To those who are called, beloved in God the Father and kept for Jesus Christ… (Jude 1:1)
Sixth and finally, the question naturally arises: isn’t there a tension between passages warning against falling away, and passages promising that Christ will hold those who are his? It seems to me that we mustn’t set these promises of God’s ‘keeping’ us, up against verses that warn against falling away, and find a contradiction. The function of both statements, in Hebrews and John’s gospel is pastoral. They each address a particular situation with a particular purpose. The book of Hebrews, for example, is written to a community that is in real danger of crowding out Christ with an over emphasis on the trappings of Judaism. For us, there are times when we are desperate to know that God is holding us. On the other hand, there are times for a warning.
 Some scholars understand the pastoral crisis facing the recipients of Hebrews differently.