- 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.