In his introductory essay to the John Milton volume of 'Bloom's Critical Views' Harold Bloom called this question
the most famous and vexing of critical problems concerning
Paradise Lost, the Satanic controversy itself. Is Satan in some sense heroic, or
is he merely a fool?
Bloom calls the former camp the 'Satanists' and the latter he calls 'Anti-Satanists'. The essay is worth reading in full; it contains many threads of inquiry into other writers. Samuel Johnson and C.S. Lewis were Anti-Satanists, for example, and Bloom identifies William Blake and Percy Bysshe Shelley as the two original Satanist readers of Milton.
Bloom said Satan
is at once the
aesthetic glory and the moral puzzle of Milton’s epic of loss and disillusion.
I am not well versed in Theology, but Bloom tries to give the basic background:
Milton believed in the doctrines of the
Fall, natural corruption, regeneration through grace, an aristocracy of the
elect, and Christian Liberty, all of them fundamental to Calvinist belief, and
yet Milton was no orthodox Calvinist,
The hope
for man in Paradise Lost is that Adam’s descendants will find their salvation in
the fallen world, once they have accepted Christ’s sacrifice and its human
consequences, by taking a middle way between those who would deny the
existence of sin altogether, in a wild freedom founded upon a misunderstanding of election, and those who would repress man’s nature that spirit
might be more free. The regenerated descendants of Adam are to evidence
that God’s grace need not provide for the abolition of the natural man.
To know and remember this as Milton’s ideal is to be properly prepared
to encounter the dangerous greatness of Satan in the early books of Paradise Lost
Bloom spends a paragraph on the Anti-Satanists:
The anti-Satanist school of critics has its great ancestor in Addison,
who found Satan’s sentiments to be “suitable to a created being of the most
exalted and most depraved nature.... Amid those impieties which this
enraged spirit utters ... the author has taken care to introduce none that is not
big with absurdity, and incapable of shocking a religious reader.” Dr. Johnson
followed Addison with more eloquence: “The malignity of Satan foams in
haughtiness and obstinacy; but his expressions are commonly general, and no
otherwise offensive than as they are wicked.” The leading modern antiSatanists are the late Charles Williams, and C. S. Lewis, for whom Milton’s
Satan is to some extent an absurd egoist, not altogether unlike Meredith’s Sir
Willoughby Patterne. So Lewis states “it is a mistake to demand that Satan,
any more than Sir Willoughby, should be able to rant and posture through
the whole universe without, sooner or later, awaking the comic spirit.” Satan
is thus an apostle of Nonsense, and his progressive degeneration in the poem
is only the inevitable working-out of his truly absurd choice when he first
denied his status as another of God’s creatures
As for the Satanists, Bloom says that no-one put it better than Coleridge, whom he quotes:
But in its utmost abstraction and consequent state of reprobation,
the will becomes Satanic pride and rebellious self-idolatry in the
relations of the spirit to itself, and remorseless despotism
relatively to others; the more hopeless as the more obdurate by its subjugation of sensual impulses, by its superiority to toil and
pain and pleasure; in short, by the fearful resolve to find in itself
alone the one absolute motive of action, under which all other
motives from within and from without must be either
subordinated or crushed.
Summing up, Bloom says:
Each reader of Paradise Lost must find for himself the proper reading of
Satan, whose appeal is clearly all but universal. Amid so much magnificence
it is difficult to choose a single passage from Paradise Lost as surpassing all
others, but I incline to the superlative speech of Satan on top of Mount
Niphates (Book IV, ll.32–113), which is the text upon which the antiSatanist, Satanist or some compromise attitude must finally rest. Here Satan
makes his last choice, and ceases to be what he was in the early books of the
poem.
Read the speech here
Suffice it to say that we will probably not get this one done-and-dusted on the literature stackexchange. That doesn't mean we shouldn't try!