The real grieving figure is that of the thousands who have simply ‘ceased to be members’. Some people say they are small loss; they can never have been really whole-hearted members. I do not believe it. Of course they were not perfect, but neither were they hypocrites. They have lost a faith which once they had, and, for this is the main point, that is something that in the future might happen to any of us. You cannot ever become so good a Christian as to be secure, beyond all fear of falling.
‘AH Lord, with trembling I confess,
A gracious soul may fall from grace;
The salt may lose its seasoning power,
And never, never, find it more’ (Charles Wesley).
This means you must watch your step when you talk about Christian certainty. Karl Barth once wrote ‘God lends people certitude, but he denies them security.’ That hits it off precisely. God be thanked for the precious loan of certitude, the joyful assurance in which we rejoice, confident that when Christ took away the sins of the world, he took away mine, and there is therefore no condemnation for those that are in Christ Jesus. But beware. The moment you see any Christian, and especially yourself turning this kind of living assurance into security, you may know that there and then he has lost the truth. There is no security but Christ, none in our learning (even in our theological learning), none in our Church and ministry, none in our virtue or religious experience. We have at once the assurance and the insecurity of faith.