In Shakespeare's The Merchant of Venice, Act Two, scene two, as Shylock's servant has a discussion with himself as to whether or not to leave his employment, the reader may well feel as if he/she is witnessing a mental tennis match. Ironically, throughout his confused internal dialogue, Launcelot actually struggles with which devil he should serve: the one he works for or the one with which his conscience is struggling.
As he begins the discussion, we learn that Launcelot is trying to do what he thinks is the best thing. While he at first states that his conscience will allow him to leave, he discovers that this is not the case. The devil is whispering to Launcelot that he should leave immediately:
The fiend is at mind elbow, and
tempts me; saying to me...use your legs, take the start, run away. (II.ii.2-3, 5)
Perhaps to Launcelot's surprise, his conscience is not telling him that he should go, but that he stay; we might infer that his conscience offers up to Launcelot the honorable path he should follow.
...take heed...honest Launcelot
Gobbo; do not run: scorn running with thy heels... (6-8)
It is again ironic that the devil calls to heaven to get Launcelot to wake up and move on.
...says the fiend, for the heavens rouse up a
brave mind, says the fiend, and run. (10-11)
Again, Launcelot struggles with a conscience that is so strong that it hangs around "the neck of my heart" (12). He does not credit that his personal sense of honor was given to him by his father, but by his mother. He wants to do what is honest: and so continues the "tug of war" as his conscience tells him not to budge, and the devil demands that he go.
By this time, it is hard to tell who is having the strongest effect on Launcelot. He notes that his conscience is giving him great advice, but that the devil is also giving him wise counsel. His conscience, he remarks, says he should continue to serve his master, Shylock the Jew. And if he were to be ruled by his conscience, it is what he would do. At the same time, however, [ironically] Launcelot acknowledges that the devil is telling him to steer clear of a man who is the embodiment—a human representation—of the devil:
...to run away from the Jew, I should be ruled by
the fiend, who...is the devil himself.
Certainly, the Jew is the very devil incarnation... (21-23)
We can imagine, then, when Launcelot decides to run away, he is listening to the devil in order to flee from a man on earth who is a devil, perhaps believing that in doing so, he is removing himself (at that moment) from the lesser of two evils. In this confused dialogue, Shakespeare offers the theme that what seems to be the proper choice because it is the socially acceptable one (to be faithful to one's master) is not always the best one (should he stay and serve a devil?). Ironically, though Launcelot believes he is ignoring his conscience that is so closely tied to his heart, he is (in fact) doing the right thing in leaving the employ of such a wicked man.