A key autobiographical element in books 1–4 in Paradise Lost involves John Milton’s eyesight. In 1652, when Milton was 43, he lost the ability to see in both of his eyes. A reader can identify several links to Milton’s blindness throughout the first four books. In book 1, Milton says, “What in me is dark / Illumine.” This connects to Milton’s real-life belief, which he articulates in his pamphlet Second Defense of the English People, that he possessed “an inner and far more enduring light.”
Milton’s confidence in his “light” and ability to illuminate things that others can’t plays a big role in the books listed in the question. In his life, Milton was not shy about asserting his superiority and calling out the inferiority of the people and world around him. In Second Defense, speaking about his blindness, Milton says, “I would rather have mine, if it be necessary, than theirs.” In another pamphlet, Of Reformation, Milton reproves priests who treat the sacrament like a “tavern biscuit.”
Milton, in real life, did not have self-esteem issues. He was sure that he enjoyed a special relationship with God and could convey things that other humans, those without his “enduring light,” could not. At the end of the first stanza in book 1, Milton writes, “I may assert Eternal Providence, / And justifie the wayes of God to men.” This could be considered autobiographical because, as Milton scholars have argued, Milton had a large enough ego to believe that he could be, more or less, God’s spokesperson.
Another autobiographical element involves politics and war. It shouldn’t be too trying to connect Satan’s conflict with God, as represented in the applicable books, to England’s civil war, which pitted King Charles I against Oliver Cromwell. The latter won, and Milton became his Secretary of Foreign Tongues. Yet Milton was not uncritical of Cromwell. Some suggest that Satan can be seen in the context of Cromwell.