WILLIAM BLAKE:

Those who restrain desire do so because theirs is weak enough to be restrained; and the restrainer or reason usurps its place and governs the unwilling.

And being restrained, it by degrees becomes passive, till it is only the shadow of desire.

The history of this is written in Paradise Lost, and the Governor or Reason is called Messiah.

And the original Archangel, or possessor of the command of the heavenly host, is called the Devil or Satan, and his children are called Sill & Death...

But in Milton, the Father is Destiny, the Son a Ratio of the five senses, and the Holy-ghost Vacuum!

Note: The reason Milton wrote in fetters when he wrote of Angels and God, and at liberty when of Devils and Hell, is because he was a true Poet and of the Devil's party without knowing it.

[From The Marriage of Heaven and Hell, ca. 1790-9 ]

PERCY BYSSHE SHELLEY:

...Milton's poem contains within itself a philosophical refutation of that system, of which, by a strange and natural antithesis; it has been a chief popular support. Nothing can exceed the energy and magnificence of the character of Satan as expressed in Paradise Lost. It is a mistake to suppose that he could ever have been intended for the popular personification of evil. Implacable hate, patient cunning, and a sleepless refinement of device to inflict the extremest anguish on an enemy, these things are evil; and, although venial in a slave, are not to be forgiven in a tyrant; although redeemed by much that ennobles his defeat in one subdued, are marked by all that dishonors his conquest in the victor. Milton's Devil as a moral being is as far superior to his God, as one who perseveres in some purpose which he has conceived to be excellent in spite of adversity and torture is to one who in the cold security of undoubted triumph inflicts the most horrible revenge upon his enemy, not from any mistaken notion of inducing him to repent of a perseverance in enmity, but with the alleged design of exasperating him to deserve new torments. Milton has so far violated the popular creed (if this shall be judged to be a violation) as to have alleged no superiority of moral virtue to his God over his Devil.

[From A Defense of Poetry, 1821]

...The only imaginary being resembling in any degree Prometheus is Satan; and Prometheus is, in my judgement, a more poetical character than Satan, because, in addition to courage, and majesty, and firm and patient opposition to omnipotent force, he is susceptible of being described as exempt from the taints of ambition, envy, revenge, and a desire for personal aggrandizement, which, in the hero of Paradise Lost, interfere with the interest. The character of Satan engenders in the mind a pernicious casuistry which leads us to weigh his faults with his wrongs, and to excuse the former because the latter exceed all measure. In the minds of those who consider that magnificent fiction with a religious feeling it engenders something worse. But Prometheus is, as it were, the type of the highest perfection of moral and intellectual nature, impelled by the purest and the truest motives to the best and noblest ends.

[From Preface to Prometheus Unbound, 1820]

SAMUEL TAYLOR COLERIDGE:

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. This is the character which Milton has so philosophically as well as sublimely embodied in the Satan of his Paradise Lost. Alas! too often has it been embodied in real life. Too often has it given a dark and savage grandeur to the historic page. And wherever it has appeared, under whatever circumstances of time and country, the same ingredients have gone to its composition; and it has been identified by the same attributes. Hope in which there is no cheerfulness; steadfastness within and immovable resolve, with outward restlessness and whirling activity; violence with guile; temerity with cunning; and, as the result of all, interminableness of object with perfect indifference of means; these are the qualities that have constituted the commanding genius; these are the marks that have characterized the masters of mischief, the liberticides, and mighty hunters of mankind, from Nimrod to Bonaparte. And from inattention to the possibility of such a character as well as from ignorance of its elements, even men of honest intentions too frequently become fascinated. Nay, whole nations have been so far duped bv this want of insight and reflection as to regard with palliative admiration, instead of wonder and abhorrence, the Molochs of human nature, who are indebted for the larger portion of their meteoric success to their total want of principle, and who surpass the generality of their fellow creatures in one act of courage, only that of daring to say with their whole heart, "Evil, be thou my good!"

[from The Statesman's Manual, 1816]

See also:

DeGivry, E. Sorcery, Magic and Alchemy. New York: Mallard Press, 1991
Greenblatt, S. Hamlet in Purgatory. Princeton: Princeton University Press, 2001
Prosser, E. Hamlet and Revenge. Stanford: Stanford University Press, 1971.
Summers, M. (ed.) The Malleus Maleficarum (of Heinrich Kramer and James Sprenger)
New York: Dover, 1971.