Admittedly we all have trouble gathering into our minds the meaning of eternal. The reason for that is because human words and our understanding of them are confined to our time and space and that does not encompass the word eternal. It has neither time nor space. About the best we can do is to use other words like timelessness, agelessness or endlessness.
Our dictionaries don't do any better. They use phrases like without beginning or end, lasting forever, perpetual or immutable. I was once told that the NT Greek word for eternal could be translated age upon age upon age upon age, etc., etc. Thayer's Lexicon of Greek Words uses the phrase "that which always has been and always will be."
Second Corinthians 4:18 records the thought "...For the things which are seen are temporary, but the things which are not seen are eternal." That might be looked at as God's way of defining eternal for us. This verse is found in the context of a discussion about the outward and inward man. These words are meant to be an encouragement to Christians in dealing with the obvious passing of time and the deterioration of our physical bodies and abilities. Such happens, it is inescapable, and we should "not lose heart" over it (4:16). To lose heart means to feel discouraged, defeated or pessimistic about our lives/ourselves.
The opposite is said of the inward man. This is our soul or spirit, that part of us that is called "the image of God" (Gen. 1:27). It is what makes us unique. It is God's gift to us making us worth more than all creation. So it is this spark of deity that 2 Corinthians 4:16 says, in contrast to the outward man, "is being renewed day by day." This is what is truly valuable about each of us. This is what we should be diligently concerned about and caring for because it is eternal. R.C.H. Lenski words it: "The inner man blossoms into new youth, beauty, and strength day by day" (Interpretation of 2 Cor., 990). We are grooming the soul for eternity.
Of course, these words are not spoken about everyone but of Christians who have fully grasped what is truly important. The trinkets of earthly life which so often attract our sight and desires are not what we are talking about. We are talking about causing ourselves to be "renewed in the spirit of our mind" (Eph. 4:23) and "in knowledge according to the image of Him who created him" (Col. 3:10). We do this when we "set [our] minds on" the things of the spirit (Rom. 8:4-5), eternal things, and "do His commandments" so that we "may have the right to the tree of life, and may enter through the gates into the city" (Rev. 22:14).
It is Jesus who in assessing the Judgment Day said, "And these will go away into everlasting punishment, but the righteous into eternal life" (Matt. 25:46). Yes, eternity is coming for each of us and it will make a huge difference as to how we have prepared for it. Are you renewing the image of God day by day? Or, are you more concerned about your physical attributes? Think about it!
- Focusing On Truth, December 2013