Milton begins his epic with an invocation addressed to the Heavenly Muse, who inspired Moses to explain how heaven and earth rose out of chaos. Accordingly, the Heavenly Muse is God, especially the Holy Spirit, who inspired Moses to write the book of Genesis.
In the invocation, Milton mentions the subject of the epic: man’s first disobedience that “brought death into the world, and all our woe, with loss of Eden, till one greater Man restore us, and regain our blissful Seat.”
Milton then introduces the creature who persuaded man to disobey God, the apostate angel, who challenged the Omnipotent to arms and consequently was cast out of heaven.
For nine days, he and his infernal crew lay vanquished, languishing in the fiery lake. In addition to the pain that he felt, the remembrance of the happiness that he had lost grieved him deeply. He looked around with dismay, mixed with obdurate pride and steadfast hate. Everywhere he saw flames that cast no light. Instead, a sort of visible darkness emanated from the flames and revealed woeful sights to the fallen angel.
The apostate angel, better known as Satan, eventually noticed that Beelzebub, his second in command, was lying next to him. After commenting on the altered appearance of Beelzebub and their glorious but unsuccessful revolt, he defiantly declared: “What though the field be lost? All is not lost; the unconquerable Will, and study of revenge, immortal hate, and courage never to submit or yield.” He resolved never to bow and sue for grace. Noting that his Empyreal substance was immortal, he was determined to wage eternal war against their Foe, employing either guile or force.
Though he spoke boldly, he felt grievous pain and was wracked with deep despair.
Beelzebub was not so confident. He observed that their Conqueror must be almighty, since only an omnipotent power could have defeated the mighty armies of Satan. He suggested that the divine Providence may have allowed them to survive with undiminished strength in order that they might feel their pain more keenly, or perhaps He wanted to use them as slaves. If so, they would not profit from their immortality in any way.
Satan scolded Beelzebub for his weakness. He would never serve God by doing good, but always irk him by performing evil deeds. He then continued with the words: “If then His Providence out of our evil seek to bring forth good, our labour must be to pervert that end, and out of good still to find means of evil; which oft times may succeed, so as perhaps shall grieve him, if I fail not, and disturb His inmost counsels from their destined aim.”
Satan noted that the thunder, the lightning, and the sulfurous hail that had pursued them as they fled from heaven had ceased. Satan suggested that they take advantage of the respite that they were enjoying. Instead of continuing to wallow in the waves of the fiery lake, he suggested that they fly to a dreary plain nearby, where they would consult on how they might offend their Enemy and repair their losses.
The huge bulk of Satan was chained to the burning lake, but the high permission of all-ruling Heaven left him at large to pursue his dark designs, in order that he might heap unto himself damnation and suffer repeated annoyance when all his malice regularly resulted in infinite goodness.
Satan left the lake and flew to dry land. His unblessed feet landed on soil that burned with solid fire, just as the lake burned with liquid fire. Beelzebub followed his master to the fiery shore.
While surveying his dismal habitation, so different from the realm of celestial light, Satan said: “Farewell happy fields where Joy forever dwells: Hail horrors, hail infernal world, and thou profoundest hell. Receive thy new possessor: One who brings a mind not to be changed by place or time. The mind is its own place, and in itself can make a heaven of hell, a hell of heaven.” He pointed out that in hell they would be free. He would rather reign in hell than serve in heaven.
Satan then summoned his followers from the fiery lake. They rose and flew to the shore. As they flew, they resembled the swarm of locusts which Moses had summoned to plague the land of Egypt.
The names of these warriors had been blotted out of the book of life because of their rebellion. Later, the descendents of Eve gave them new names and worshiped them as idols. Among them was Moloch, a horrid king besmeared with the blood of human sacrifice, to whom the Ammonites sacrificed children. Also present were Chemosh, the god of the Moabites; Dagon, the god of the Philistines; Rimmon, the god of Damascus; Osiris, Isis, and Horus, gods of the Egyptians; and the numerous gods of ancient Greece. The host also included Thammus and various Baalim and Ashtaroth, deities of Mesopotamia. Last of all came Belial, the most lewd spirit that fell from heaven. No altar was ever dedicated to him, but his sons roamed the streets of Sodom and Gibeah in the tribe of Benjamin.
When they came to shore, they organized themselves in military array, with their banners held high. Satan looked at his hosts with pride and began to speak.
In his speech, he expressed the hope that his mighty hosts might some day repossess their native seats. However, since they now knew how strong the Almighty was, he considered it prudent to use guile instead of force while endeavoring to attain their goal.
Satan had heard that God was planning to create a new world. He figured that he and his host might attempt to take over this new creation. He considered it certain that hell would not retain his mighty hosts forever. Either in the new world or elsewhere, they would eventually find a better home.
In response, the fallen angels drew their flaming swords and hurled defiance toward the vault of heaven.
The demons soon discovered that there was plenty of gold in the soil of hell. Led by Mammon, the least upright of all the fallen angels, they began an extensive mining operation.
When sufficient materials had been extracted from the soil, they erected an edifice far more excellent than the buildings that the Babylonians and Egyptians dedicated to their idols. The reprobate angels built this building in an hour. Mulciber (Hephaestus) was their architect. They called the structure Pandemonium. It became the high capital of Satan and his peers.
After the structure was finished, all the fallen angels were summoned to Pandemonium for a conference. They were all huge creatures, so they did not fit comfortably when they entered the building. Therefore, when the signal was given, they all assumed a diminutive stature. They became small as elves. Book one of Paradise Lost concludes with the words: “After short silence then and summons read, the consult began.”
Literature.Org: Paradise Lost