FAUSTUS
[To Emperor.] My lord, I must forewarn your Majesty,
That when my spirits present the royal shapes
Of Alexander and his paramour
Your Grace demand no questions of the King,
But in dumb silence let them come and go.
[…]
These are but shadows, not substantial. (4.1.90-94, 101)
Oh so Faustus's powers do have limits: he isn't able to conjure the real Alexander and Darius—just their shadows. So then what's the point of giving the gift of conjuring to these guys if their figures can't be questioned or even touched? Is the point just to delight and entertain? Is that really worth handing over your soul?
Quote 26
FAUSTUS
My gracious lord, not so much for injury done to me as to delight your Majesty with some mirth hath Faustus justly requited this injurious knight; which being all I desire, I am content to remove his horns. Mephistopheles, transform him. [Mephistopheles removes the horns.] (4.1.153-157)
Faustus is being quite the suck-up here, brownnosing the Emperor by claiming that everything he does is for his delight. We know that Faustus's giving Benvolio horns is as much for petty vengeance as for anything else. But even if it is just to amuse the emperor, is that an honorable reason to humiliate someone?
Know you not, traitors, I was limited
For four-and-twenty years to breathe on earth?
And had you cut my body with your swords,
Or hewed this flesh and bones as small as sand,
Yet in a minute had my spirit returned,
And I had breathed a man made free from harm. (4.3.71-76)
It's interesting that Faustus characterizes himself as "limited" to twenty-four years of life, especially when the argument he wants to make is really about how powerful he is. Maybe Faustus is finally realizing just how much his pact with the devil is going to cost him.