Book 1 - Knowledge of God the Creator
Chapter 15 - Of Human Nature, the Soul, Image of God, Free Will
Sections 1-4 - Man's nature deformed; yet his soul bears, though almost obliterated, the image of God
Section 1 - Man proceeded spotless from God's hand; therefore he may not shift the blame for his sins to the Creator
We have to know both what we were like before sin, and what we are like in sin (after the Fall).
If we blame our faults on nature, not ourselves, we are blaming God.
Our pride is curbed, in that we are of clay (Gen 2:7; 18:27; Job 4:19); yet God has given us an "immortal spirit," so we glory in God's generosity.
Section 2 - Diversity of body and soul
The soul is an immortal yet created essence.
Ecc 12:7; Luke 23:46; Acts 7:59.
The conscience is a sure sign of its existence.
As is mental activity and dreaming while sleeping.
Were the soul not an essence on its own, these verses wouldn't make sense: Job 4:19; 2 Cor 7:1; 1 Pet 2:25; 1:9; 2:11; Heb 13:17; 2 Cor 1:23; Matt 10:28; Luke 12:5; Heb 12:9; Luke 16:22-3; 2 Cor 5:6, 8; Acts 23:8.
Section 3 - God's image and likeness in man
God's image is primarily spiritual, less so physical.
God's image in man is not physically from Christ's incarnation.
But His likeness extends to all aspects of man.
Image and likeness refer to the same thing.