...the existential dimension was never eliminated from the film. In fact, one of the few scenes written for Taxi Driver during its production provides the most heavy-handed example of European existentialism in the film. As it happened, Peter Boyle, the ex-Christian Brother [i.e., a member of the order of Brothers of the Christian Schools, a Catholic order] who plays Wizard, an elder statesman cab driver whom Travis turns to for advice, had been part of the rat pack in the Phillipses' salon One afternoon he mesmerized the sandal set with an improvisation as Jesus Christ, the standup comedian in a tawdry Las Vegas piano bar. [Paul] Schrader and [Martin] Scorsese, two altar boys at heart, never forgot this semi-blasphemous display and wanted Boyle to work on Taxi Driver. Boyle chaffed at Wizard's limited lines, however, so Schrader wrote a new shtick especially for Boyle, a cut-rate philosophical rap positing that existence precedes essence.