Milton addresses the light emanating from Heaven, saying it is God's first "offspring." This is the second invocation of the poem.
The poet is now revisiting Heaven, after having spent the first two books in Hell.
He still feels the heavenly light, but he can't see it because he's blind. This doesn't prevent him from writing poetry, however. He's too tough for that.
The poet hasn't forgotten about other famous blind poets and prophets, such as Homer and Tiresias; he's "equal" to them in blindness and hopes to be "equal" to them in fame.
The poet can't see anything so he asks the "celestial light" to shine inward – i.e., give him some kind of mental vision so he can compose poetry and talk about things that most humans can't see anyway (Heaven, Hell, the past, etc.).
God is in Heaven, looking down at his angels, at Adam and Eve, and at Satan. His Son (not named Jesus yet) sits on his right.
God describes Satan's malice to His Son. God knows what he's (Satan) up to, and he knows that Satan will succeed in his attempts to tempt mankind.
Everyone – man and angels included – has a choice. If they didn't have a choice, their obedience to God would be a joke; it wouldn't be meaningful.
God stresses that predestination doesn't exist; both mankind, Satan, and the other rebel angels fell by their own choice: "they themselves decreed/ Their own revolt, not I" (3.116-7).
Because mankind was deceived, he will find grace at some point. Satan and company will get nothing.
God's Son responds. He praises God's resolution regarding man (i.e., that he will have grace) because it simply isn't possible that Satan should win.
God responds, telling his Son that he's read his mind exactly. Some men will be saved, but not because of their own will but because of God's grace.
God says everyone will have the ability to hear his call; he'll implant a conscience in them, which will help them achieve grace, Heaven, or whatever safely.
But wait, what about all of man's sins? They have no way of making up for those, unless someone will become mortal and die for their sins. Any volunteers?
Heaven stands "mute." Nobody wants to make the sacrifice. This could have been the end for mankind if the Son hadn't stood up.
He'll do it; he'll become mortal and die for man's sins.
The Son says he knows he'll be giving up a lot in Heaven, but he also knows that he won't really die (he's immortal after all).
He'll rise from the dead, defeat Satan and death itself, and lead Hell captive. Then he'll return to Heaven.
God responds to the Son, saying essentially "thank God for you my Son, otherwise man would have been toast."
The entire human race will be saved through the intercession of his Son, and through him only.
The Son won't degrade himself by becoming a man, says God; so great a sacrifice will do nothing but exalt him.
Moreover, He will then make his Son sole ruler of the universe. "All knees to thee shall bow, of them that bide / In Heaven, or Earth, or under earth in Hell" (3.321-322).
God continues, saying that eventually there will be a Last Judgment ("doom") when the Son will send some people to Hell and some to Heaven.
After that, Hell will be closed off completely, the earth will be burned, and a new Heaven and earth will emerge.
All Heaven resounds with hymns of praise, cheering, and "jubilee." The angels bow down before God's and the Son's thrones, before picking up their harps and making music.
The narrator tells us that the Son is God's agent; it was through the Son that he created the universe and through him that he defeated the rebel angels.
Meanwhile, Satan emerges from Chaos at the outer edge of the created universe.
He's like a vulture in the Himalayas who can't find any food so he goes in search of more fertile pastures but then stops off in a barren region.
From his position he can see Heaven's gate – it is made with diamonds, gold, and other jewels – and a set of stairs that go from the created universe up to Heaven.
At the bottom of the stairs is a portal that opens into the universe; Satan looks through the portal, almost as if he had been hiking all night and finally got to the top of a hill from which he could see an entire land or city, glistening in the dawn's light.
Satan doesn't stick around to enjoy the view but flies right through the portal. He lands on the sun! It's really bright – "beyond expression bright" – and colorful.
Satan looks around the universe – it's always sunny, no shade yet. He sees an angel in the sun with his back turned and a tiara on his head. He looks busy, or at least as if he's thinking deeply.
Satan quickly changes his appearance; he turns into a young Cherub (a different order of angel) and approaches the angel, who turns around when he hears Satan approaching.
It's Uriel, one of the seven angels who stand closest to God's throne. Satan addresses him, saying he wants to check out God's new creation. He asks him which planet is man's.
Uriel – who can't tell he's being duped – responds to Satan, saying there's nothing wrong with wanting to see God's creations.
Uriel himself saw the world created; he points out the location of Paradise (i.e., the Garden of Eden) for Satan, who thanks him and heads towards the earth, landing on Mt. Niphates.