Question: : What is the best way to explain the differences in our soul and spirit? And what happens eternally?
Answer:If you do a study of the use of the words “soul” (Hebrew, nephesh, Greek, psuche) and “spirit” (Hebrew, ruach, Greek, pneuma), I believe you will find that they are used interchangeably as a description of what gives life to the body and bears the aspects of personality in human beings. For example, Mary said in Luke 1:46-47, “My soul maginifies the Lord, and my spirit rejoices in God my Savior,” using the typical Hebrew poetic device of parallelism, where the first phrase is repeated using different but synonymous terms in a second phrase. People who have died and gone to heaven or hell can be called either spirits (Hebrews 12:23; 1 Peter 3:19) or souls (Revelation 6:9; 20:4).
But what then do we do with passages like 1 Thessalonians 5:23, “May the God of peace himself sanctify you wholly; and may your spirit and soul and body be kept sound and blameless at the coming of our Lord Jesus Christ”? It is most likely that Paul is talking about our sanctification in more emphatic terms by adding terms to the description. When Jesus said we were to love God with our hearts, souls and minds, he did not mean that there are three distinct parts to the inner man (leaving out spirits), but that we were to love God with every aspect of our being. Since spirit and soul are two interchangeable ways of speaking about the inner man he includes both here for emphasis.
Hebrews 4:12 is another passage which seems to separate soul and spirit as different entities, saying that the Word of God is able to penetrate “even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart.” Again, if we include heart in this discussion we end up with three inner parts to mankind. But the author of this passage is more likely speaking about how the Word of God exposes the inner workings of our motives located in various aspects, not entities, of our inner being, including even the most inner parts of our joints and marrow, viewed as seats of our emotions and thinking.
From the standpoint of what happens eternally, we know that the soul/spirit separates from the body at death (James 2:26; Philippians 1:21-26) and goes immediately to either Hades (if you do not know Christ) or heaven (if you do know Christ) and remains there until the resurrection of the body (1 Thessalonians 4:13-18) when Jesus will bring the souls of those who have died in him to earth to be reunited with perfected bodies. The resurrection, which is the joining of a perfected spirit/soul and perfected body, is one of the most important doctrines in the Christian faith (1 Corinthians 15). We are not meant to be disembodied spirits for eternity.
Wayne Grudem’s, Systematic Theology, is an excellent source for this topic and others.