Although today's verse appears in parentheses in the King James Bible, it is a most important concept in Scripture and is the summary of an extensive passage which precedes it. Beginning with 2 Corinthians 4:8, Paul continually contrasts the seen and the unseen, finishing up with the admonition to "walk by faith."
"We are troubled on every side, yet not distressed; we are perplexed, but not in despair; Persecuted, but not forsaken; cast down, but not destroyed" (vv. 8-9). Though we have trials on the outside, through faith we have inward triumph.
"Always bearing about in the body the dying of the Lord Jesus . . . that the life also of Jesus might be made manifest in our mortal flesh" (vv. 10-11). Even though "death worketh in us," that same persecution results in "life in you" (v. 12). Through faith we know "that he which raised up the Lord Jesus shall raise up us also by Jesus" (v. 14).
"Though our outward man perish, yet the inward man is renewed day by day. For our light affliction, which is but for a moment, worketh for us a far more exceeding and eternal weight of glory" (vv. 16-17).
"If our earthly house [i.e., body] of this tabernacle were dissolved, we have a building of God, an house not made with hands, eternal in the heavens" (5:1), "that mortality might be swallowed up of life" (v. 4). The death and decay of this life will ultimately be eradicated. We know this to be fact, for He "hath given unto us the earnest of the Spirit" (v. 5) as a guarantee of our resurrection, if indeed we have been born again by faith, the same faith by which we walk.
"While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal" (2 Corinthians 4:18). JDM