A brief encapsulation of Faustus's mental conflict begins with the description given by the Chorus in Act I, scene i of Dr. Faustus and ends with the Chorus's summary of his plight. The Chorus begins with a metaphor that compares Faustus to Icarus who fatefully flew too near the Sun on waxen wings. They say that Faustus is "glutted now with learning's golden gifts" and therefore turns to gorge himself on magic: "He surfeits upon cursed necromancy; / Nothing so sweet as magic is to him" (surfeit: an amount of something that is too large).
Faustus's initial mental conflict is to find something to inspire him that is worthy of professing, since he is at the end of his greatly prolonged studies: “begin / To sound the depth of that thou wilt profess.” He rejects the study of logic ("Analytics"), economics, medicine, law, and divinity: “What will be, shall be? Divinity, adieu!” He settles upon magic and the "necromantic books" that will bestow him with power and profit and command of "All things that move between the quiet poles" [North and South Poles]:
O, what a world of profit and delight,
Of power, of honour, of omnipotence,
Is promis'd to the studious artizan! ...
His mental conflict at the end of the play has done a turn-about because he has found that even the power Mephistophilis could give was no comparison to the loss of "eternal joy and felicity." Nor could it compensate for the "ireful bow" of God and the torment of eternal suffering. His mental conflict is illustrated three ways. Firstly, his talk with the Old Man draws Faustus toward pleading repentance before God--but Mephistophilis comes, and Faustus yields to the pain and to the fear of pain of present suffering (had he but braved the present suffering to plead with God for mercy!).
Secondly, he confesses to the Scholars, who adjure him to plead for God's salvation to which Faustus replies that his arms are held down and his heart is ripped to pieces if he but names the name of God--he yields to the conflict of present pain even in the face of greater future pain in eternity! Thirdly, in his speech, when left alone by the (cowardly) Scholars, he pleads with God to at least shorten the time of his eternal suffering--which he realizes can't be done. His final outcry before seeing Mephistophilis come to take him away is, "I'll burn my books!" This takes the conflict full circle to the beginning conflict that concerns which set of books Faustus should give his allegiance to. Marlowe demonstrates that Faustus chose the wrong set. The Chorus sums it up:
Faustus is gone: regard his hellish fall, / ... / Only to wonder at unlawful things / ... / more than heavenly power permits.