"The transforming 'moment' of this encounter cannot be quantified by the measurements of earthly time. It is, indeed, not eternal but a transition, and yet trying to qualify it as of 'short' or 'long' duration on the basis of temporal measurements derived from physics would be naive and unproductive. The 'temporal measure' of this encounter lies in the unsoundable depths of existence, in a passing-over where we are burned ere we are transformed. To measure such Existenzzeit, such an 'existential time,' in terms of the time of this world would be to ignore the specificity of the human spirit in its simultaneous relationship with, and differentation from, the world.
. . .
"[Purgatory] is the inwardly necessary process of transformation in which a person becomes capable of Christ, capable of God and thus capable of unity with the whole communion of saints.
. . .
"Encounter with the Lord is this transformation."...
--Joseph Ratzinger, Eschatology: Death and Eternal Life, p. 230-231