Milton also tells us the subject of his poem is the original sin committed by Adam and Eve, the eating of the apple from the Tree of Knowledge. Because of this sin, mankind must now suffer death and wait for Jesus to return in order for humans to be restored to a state of purity.
The muse Milton calls upon is not the nine classical muses, but it is the muse of the Holy Spirit, the same one who inspired Moses to write Genesis. Because he's invoking the Holy Spirit to help him, Milton says his poem is greater than any poem written by the classical poets, such as Homer or Virgil. He asks the Holy Spirit to tell him about the world's beginning so he can reveal to humans that the fall of Adam and Eve was a part of God's greater plan. "That, to the height of this great argument,/I may assert Eternal Providence,/And justify the ways of God to men." Milton is justifying God's plan of having Adam and Eve committ the original sin. His poem will also be greater because it deals with a more important subject.
Milton begins his poem humbly and ambitiously. His humility is shown by his dependence on God's grace to speak through him. His ambition is to surpass the poems of the classical poets. He shows respect to the poets, such as Homer, but he also promises to outdo them. In essence, he's reinventing Classical literature by writing it from a Christian perspective, explaining God's plan for humans. Milton intends for his poem to be the first English epic.
Raised Catholic for most of his life, Milton converted to Protestantism in his twenties, and had planned for years to write an Epic poem. In this work he expresses, publicly, his views on religion. By the time he had written this famous piece, the Anglican Church, or Church of England, had already split into various sects. Milton, himself, was a Presbyterian. Milton despised the corruption he saw in the Catholic Church, and he frequently attacked it through his poetry and prose. In Paradise Lost, Book IV he depicts Catholics as Satan leaping over walls. The purpose of Milton’s Paradise Lost is multifold actually; it can be observed as a highly individualized personal view of Christianity while it also may be viewed as a universal political statement.
In Book I John Milton calls upon the muses to inspire him so that he “may assert th' Eternal Providence, / And justify the ways of God to men” (25-26). In other words, as a minister and as a poet, he writes the poem to explain why we must obey God. Interestingly, Satan, as a rebel and existential hero, is a more interesting and complex character than God, which would seem to undermine Milton’s stated purpose. We can explain this in terms of the politics of the 17thC when he wrote the poem, for during this time Milton, in the spirit of the Enlightenment, supported the political revolt against Charles I, believing that we have a right to disagree with forms of worldly governance Through the careful contrast of logic as disparately manifested by God and Satan, Milton reveals that conformity to God is natural and any other form of obedience is fallible.
It may seem ironic, but Milton's purpose in writing this epic is not only to give a detailed description of the dark side of creation, but to use the depravity of Satan and man to persuade people to come into the light of salvation (Eternal Providence). He wanted people to know how bad Hell really was and that it's never worth it to contest with the almighty God. He suggests that no one will ever be able to conquer him, in order to "justify the ways of God to men."