By the portion of the MSS.

relating to Milton's drafts of projected poems, which date about 1640-1642, we see that the form of his work was to have been dramatic, and that, in respect of subject, the swift mind was divided between Scripture and British History.

No fewer than ninety-nine possible themes--sixty-one Scriptural, and thirty-eight historical or legendary--are jotted down by him.

Four of these relate to "Paradise Lost." Among the most remarkable of the other subjects are "Sodom" (the plan is detailed at considerable length, and, though evidently impracticable, is interesting as a counterpart of "Comus"), "Samson Marrying," "Ahab," "John the Baptist," "Christus Patiens," "Vortigern," "Alfred the Great," "Harold," "Athirco" (a very striking subject from a Scotch legend), and "Macbeth," where Duncan's ghost was to have appeared instead of Banquo's, and seemingly taken a share in the action.
"Arthur," so much in his mind when he wrote the "Epitaphium Damonis," does not appear at all.

Two of the drafts of "Paradise Lost" are mere lists of _dramatis personae_, but the others indicate the shape which the conception had then assumed in Milton's mind as the nucleus of a religious drama on the pattern of the mediaeval mystery or miracle play.
Could he have had any vague knowledge of the autos of Calderon?
In the second and more complete draft Gabriel speaks the prologue.