I've found it to be very important to understand the make-up of man.
Some churches teach that man is a dichotomy: Body and soul.
Some teach that man is a trichotomy: Body, Soul and Spirit.
I believe it's clear that man has a a body, a soul and a spirit.
Understanding this helps us to understand how God lives in us.
To use the O.P.'s verse of 1 Thessalonians 5:23, we could view the trichotomy this way:
The body is physical and material. The bible calls it dust that will one day return to the earth. Ecclesiastes 12:7
It is neither righteous nor evil; it is amoral.
Our bodies are not perfect. They will become perfect, soma pneumatikon - spiritual bodies - 1 Corinthians 15:44.
It will experience weakness, sickness, fatigue. It is mortal, Hebrews 9:27
The soul is made up of the
mind, the emotions, the will. The soul functions overlap each other. For instance, your mind function can be influenced by your emotion. The Greek word: Psuche means soul. The soul is amoral.
The Mind:
The capacity to think and reason. There is nothing righteous or evil in learning that two plus two is four, or that the sun is shining
Emotions:
The capacity to experience feeling. Emotion itself has nothing to do with morality. You are surprised when given a surprise birthday party. You are grieved when a pet dies. This is neither good nor bad.
The Will:
The capacity to choose or to desire. The function of the will is amoral. You can choose to put ketchup on your potatoes, or to set your alarm clock for a certain time.
The Spirit: Is that part of us that connects to God. It is
moral, perfectible and immortal.
In scripture Spirit and Heart are used interchangeably.
A difference between the soul and the spirit is apparent, Hebrews 4:12
James tells us that the body without a spirit is dead, James 2:26
When we die our spirit will return to God who gave it, Ecclesiastes 12:7
Jesus yielded His spirit, Mathew 27:50
And when not in alignment with God, it can be troubled, Genesis 41:8
It Is Moral:
It is the center of the seat of the basic moral affections of man. Genesis 8:21
The Lord searches all hearts and understands intent, 1 Chronicles 28:9
With the heart, man believes, Romans 10:10
The heart, or spirit, deals with moral issues and thus it is intertwined with the soul of man.
There are some emotions which will be affected by the spirit, or lack thereof. There are some choices which will have everything to do with morality and the spirit, or lack thereof, will affect them. The lack would be a spirit lacking God. The heart or spirit is the control room where either Christ is in command or sin is in command.
It Is Perfectible:
Mathew 5:48 Be perfect as your Father in heaven is perfect. Jesus meant this as a goal for now, something to work toward. If Jesus lives in us, the moral intent will be will be based on the purity of Jesus living in us via the Holy Spirit. The intent is love. 1 John 4:8-17 God is love...
It Is Immortal:
This "God part" of man will live on forever.
It's important to understand that our spirit is intertwined with the soul and that many soul functions can become moral when the spirit of man is considered.
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