What is the theme of the Play Dr. Faustus?

In so far Doctor Faustus (Chirstopher Marlowe) is a Christian play, it deals with the themes at the heart of Christianity’s understanding of the world.
- First, there is the idea of sin, which Christianity defines as acts contrary to the will of God.
- In making a pact with Lucifer, Faustus commits what is in a sense the ultimate sin: not only does he disobey God, but he consciously and even eagerly renounces obedience to him.
- Doctor Faustus, a well-respected German scholar, grows dissatisfied with the limits of traditional forms of knowledge—logic, medicine, law, and religion—and decides that he wants to learn to practice magic.
- His friends Valdes and Cornelius instruct him in the black arts, and he begins his new career as a magician by summoning up Mephastophilis, a devil. Despite Mephastophilis’s warnings about the horrors of hell, Faustus tells the devil to return to his master, Lucifer, with an offer of Faustus’s soul in exchange for twenty-four years of service from Mephastophilis.

Cristopher Marlowe was the greatest dramatist before Shakespeare.
- Christopher Marlowe, (baptized Feb. 26, 1564, Canterbury, Kent, Eng.—died May 30, 1593, Deptford, near London), Elizabethan poet and Shakespeare’s most important predecessor in English drama, who is noted especially for his establishment of dramatic blank verse. 

Some of Marlowe's literary works:
- Doctor Faustus,
- The Jew of Malta,
- Tamburlaine the Great

Source: Britannica.com and Sparknotes.com