In 2 Corinthians 4:18, if you're reading the King James Version, Paul seems to be comparing time with timelessness. The KJV reads here, "That which is seen is temporal, yet that which is not seen is eternal."
If "temporal" is the correct translation of the Greek word proskairon in the first clause, then "eternal" is appropriate in the second clause. But guess what? "Temporal" is a faulty translation. The right translation of proskairon in the first clause ("temporary") makes way for the right translation in the second clause ("eonian").
Who cares? Not only is this another grammatical fact piercing the hull of the eternal torment battleship, but understanding the proper translations here will comfort you as to the nature of the future eons you will inhabit.