Thoughtful Christians have always struggled with the usual Evangelical assertion that all that Christians need to be better off is to die. “Absent from the body, present with the Lord.” (2 Cor 5:8) Different states of sanctification seem have no bearing. We, like an electron, jump from one state to another without a trace of journey.
What makes this possible according to the formula is the imputation of Christ. Is this what the author of Hebrews means in writing “without holiness no man shall see the Lord.”? (Hebrews 12:14) CS Lewis thought not. His thought is that one must actually BE holy. In fact, he asserts in Letter to Malcolm that our souls demand a purgation from all actual sin, a bath, as it were, to remove the stain of our pollution. For imputation does not actually remove sin. It covers it.
Lewis rejects the Romish doctrine of purgatory as retributive, undergoing the just deserts of sin. But he apparently sees that there is some need of a full sanctification since no evil can appear in the presence of God. Jerry Walls tries to make CS Lewis’ case here. It seems that John Henry Newman’s restatement on purgatory was of some assistance to Lewis.
See Jerry Wall’s presentation that explores this.