Fwe say that we have no sin we deceive ourselves, and there’s no truth in us.” why then, belike we must sin and so consequently die. ay, we must die an everlasting death. what doctrine call you this, che sera sera, "what will be shall be? " divinity, adieu (scene 1, lines 42–45) what is the significance of these lines from the play?

The significance of the lines in this excerpt is that Faustus does not truly understand Christianity because he thought that religion was only deadly but not forgiving, for comitting a sin meant to suffering a permanent death; additionally, througout these lines Faustus showed Christianity in a negative light, so he only addressed the vengeful side of this religion.