Man curved in on himself

I've been wondering about the origin of this definition of sin for a while. Kelly Kapic unpacks it.

First Augustine identified that we stop loving God and start loving his material gifts:

"St Augustine spoke of sin as that which bends or curves us to the ground, making us more like the beasts and less like the God whom we were to image. He speculated that we were created to have our heads and hearts raised toward Yahweh, and that sin is that which turns our gaze from him."

Then

Martin Luther picked up this imagery in the Reformation, arguing that sin actually bends or curves us upon ourselves (homo incurvatus in se). We were disigned to embrace God and others, but instead we are now consumed with ourselves.

(p. 37, Kelly M. Kapic, With Justin L. Borger, God So Loved, He Gave: Entering the Movement of Divine Generosity)

So we stop loving God and start loving ourselves. Finally, Melanchthon made the further step of locating that work in the heart.