Developing (or Dynamic) Character versus the Static Character:
Adam is definitely a Dynamic Character. He undergoes a serious and permanent change. He, dragging all of mankind with him, becomes tainted by sin.
The same is true for Eve. Her original sin leads to the fallen state of ALL of mankind. Before she was an innocent women living in blissful paradise when the temptation of sin changed her life and the lives of all humans forever.
I think that Satan is more of a Static Character throughout the book. Paradise Lost starts with Satan already in his fallen state, therefore although he goes through continual mood swings, I don’t think his true evil character ever really changes. The most permanent change in Satan’s life (Satan being cast out of Heaven) has already happened before the book starts.
I think that Paradise Lost definitely sticks to the theme “Of Man’s first disobedience” and all that surrounds it.
“Of Man’s first disobedience, and the fruit
Of that forbidden tree whose mortal taste
Brought death into the World, and all our woe,
With loss of Eden,”
Everything is tied together in an effort to show how “The Loss of Eden” came about and the effects it has on mankind and the spiritual world.