SECOND SCHOLAR
Yet, Faustus, look up to heaven and remember mercy is infinite.
FAUSTUS
But Faustus' offence can ne'er be pardoned.
[…]
SECOND SCHOLAR
Yet, Faustus, call on God.
FAUSTUS
On God, whom Faustus hath abjured? On God, whom Faustus hath blasphemed? O my God, I would weep, but the devil draws in my tears. Gush forth blood instead of tears! Yea, life and soul! O, he stays my tongue! I would lift up my hands, but see, they hold 'em, they hold 'em.
ALL
Who, Faustus?
FAUSTUS
Why, Lucifer and Mephistopheles. O, gentlemen, I gave them my soul for my cunning! (5.2.39-41, 53-61)
Okay, so according to Dr. F, God can't pardon his sins. Yet in attempting to call on God, to weep tears of repentance, and to lift his hands to heaven, Faustus shows that he does believe in the possibility of forgiveness. It's just that he is unable to feel the true repentance that would set the forgiveness wheels in motion. Faustus also implies, however, that Mephistopheles and Lucifer have somehow trapped him.
THIRD SCHOLAR
'Tis but a surfeit, sir; fear nothing.
FAUSTUS
A surfeit of deadly sin that hath damned both body and soul. (5.2.36-38)
When Faustus complains that he's sick, the Scholars, drawing upon their medical knowledge, conclude that Faustus probably has an excess of something in his body. Back then, they thought that an excess of something like blood or bile was the root cause of a disease. Faustus turns their idea on its head, though, by acknowledging that he possesses an excess—of deadly sin, that is.
SCHOLAR
Well, gentlemen, though Faustus' end be such
As every Christian heart laments to think on,
Yet, for he was a scholar once admired
For wondrous knowledge in our German schools,
We'll give his mangled limbs due burial,
And all the students, clothed in mourning black,
Shall wait upon his heavy funeral. (5.3.13-19)
It's ironic that the scholarly learnedness Faustus scorned in the beginning of the play is the very ability for which he is now remembered after his death, and the one that will bring "all the students" to his funeral. This passage suggests that Faustus had the wrong priorities all along. He had a pretty sweet deal at the beginning!