What is the essence of Satan's character and what is his greatest skill, especially with respect to Book I of Paradise Lost?
Satan is arguably the most interesting, perhaps the most sympathetic, character in Paradise Lost (1667 in 10 books; 1674 in 12 books). Although Milton casts him as the antagonist against Adam and Eve, and he clearly embodies several seriously negative traits (e. g., pride, anger, resentment), Satan also demonstrates leadership and rhetorical skills unrivaled in English literature. John Dryden and many later writers, especially the Romantics, thought that Satan is the poem's true hero, an unlikely role for a character introduced as "The infernal serpent" (I. 34).
Whether we view Satan as hero or the Father of Lies, Milton characterizes him as the ultimate (and inevitable) failure:
He trusted to have equalled the most high . . . and with ambitious aim/ Against the throne and monarchy of God/ Raised impious war in heaven and battle proud/ With vain attempt. . . . (I. 40-44)
As many commentators have noted, Satan's sin is not the desire to rise above the other angels but his attempt to set himself above God--in secular terms, Satan is guilty of trying to overthrow rightly constituted authority not because the authority figure (God) is corrupt or has betrayed his people but because Satan simply believes his strengths are superior to God's. In Milton's view, Satan's greatest strengths--his ability to lead and to motivate--are also the greatest elements of corruption because they lead him to a sense of pride that blinds him to the value of a relationship with God. As he moves away from God, Satan must also destroy God's greatest creation, mankind.
While condemning Satan for his pride, Milton has created a character whose belief in freedom of will and action is incredibly appealing. Surrounded by his fallen troops who, along with him, have been cast out of heaven, Satan rallies his troops by pointing out that they are no longer physically and spiritually dependents of God:
The mind is its own place, and in itself/can make a heaven of hell, a hell of heaven. . . . Here at least/We shall be free . . . . Here we may reign secure, and in my choice/To reign is worth ambition though in hell:/Better to reign in hell, than serve in heaven. (I. 254-264)
Of course, one could argue that reigning in hell or serving in heaven are essentially false equivalencies, but one cannot argue with Satan's premise that "the mind is its own place," by which he means that he and the other fallen angels are now free to create their own reality which, in his view, is preferable to a reality over which they have no control. In just a few lines, Satan's rhetorical skills, founded on his intellectual convictions, have raised the mind's creative power over that of God, a very revolutionary concept and one that appeals to many, if not most, of Milton's readers.