Determination of eternal beginnings
The mansions of hell, no less than the mansions of heaven, are not makeshift shacks thrown up after the darkness of death has come down upon life. Both are built slowly, carefully, stone by stone, through all the abundant moments that measure the length of a man’s life. A man does not achieve hell by a last minute quirk of divine judgment, but when he embraces sin; a man does not win heaven when God embraces Him eternally but when he embraces God despite the alluring promises of all that is contrary to God. Heaven or hell, in other words, never comes as a shock; it is the harvest that was planted so long ago, watched, cultivated, defended and now reaped in all its fullness. It is the house at the end of the road that could lead nowhere else. In the case of heaven, it is home; and all along the road there were signs marking the path, help proferred to pilgrims, and directions to be had for the asking. Arriving there, man has come home to the God Who made him.
From Walter Farrell, O,P., Companion to the Summa, CHAPTER XX — ETERNAL BEGINNINGS (Suppl., Q. 92-99).