The most important element of the morality play in Doctor Faustus is its teaching of moral lessons to its audience. In telling the tragic tale of Dr. Faustus, Marlowe aims to warn us of what can happen if we turn away from God and embrace the Prince of Darkness. Faustus may very well enjoy twenty-four years of unimaginable power, wealth, and knowledge, but none of that will avail him anything when he's cast down into the fiery pit of hell.
Although it may be tempting to turn our backs on God and spend what little time we have left on this earth indulging our every whim, such temptation must always be resisted. Marlowe's abiding message, a message conveyed in countless other morality plays, is that we can run from God, but we certainly cannot hide.
Closely allied to the teaching of right and wrong is the struggle between good and evil. Like most people, Faustus is neither wholly good nor wholly evil, but an amalgam of the two. The epic battle between good and evil in Faustus's soul is personified by the Good Angel and the Bad Angel, who each try to push Faustus in a certain direction. In the kind of allegory common in a morality play, the Good Angel represents Faustus's desire to repent, whereas the Bad Angel represents his desire to keep on sinning, to keep on enjoying the power and prestige that his deal with Lucifer has brought him.