Episode 2 made it clear that Fox’s The Exorcist is a television show at war with itself: its protagonists are Catholics, but it demonstrates animus toward the Catholic Church. The theme has been carried over into Episode 3, making it central to the story. Spoilers await below.
This episode was in large part about Father Marcus, which is a problem because the character is entirely unlikable. In an early scene, Marcus shows his disrespect for Father Tomas’s church by eating corn on the cob in the pews. Later, when the Rance family has him look at Casey’s bedroom, he rifles through her belongings like a narcotics cop with a search warrant, treating the Rances with the same contempt that he showed the church. In his interview with Casey he demonstrates absolutely no compassion for her, conducting a Hannibal Lecter-like examination of her psyche. I understand that his intent was to provoke the demon inside of her, but wouldn’t it have made things more interesting if he had shown some measure of regret or disgust at what he had to do to make the demon manifest? The intensity of the scene was undercut by the unintentionally hilarious line, “Give me some sign of your presence,” while pictures are dropping to the ground and papers are flying in a telekinetic wind (compare it to this scene from The Man With Two Brains). Was the later scene of Marcus telling the stained glass image of Jesus Christ to “shut up” supposed to be shocking? It seemed like the sort of thing he does every day.
Don’t worry about his excommunication, though: it’s a good thing. The Catholic Church may be “compromised,” according to Father Bennett, so Marcus is now free to engage in exorcism without all those church people getting in his grill and messing up his style. Beats having to follow rules that he didn’t respect anyway.
Sibling rivalry was the other big theme of this episode, though it’s hard to take it seriously when the show has given us so little reason to care about what happens to Casey or Kat. Casey’s change from nice girl to malicious possessed doesn’t work: we didn’t see her enough in the beginning for the transformation to evoke much pathos. Between her breaking the other girl’s leg in the previous episode and going completely crazy on the train molester in this episode, she comes off more like Carrie than an innocent girl possessed by a horrible demon. (For a laugh, check out this IMDB thread: the subway scene had the desired “You go girl!” effect on a certain segment of viewership.) If the demon isn’t there to degrade Casey, to make her do and say things that humiliate and disgust her and turn her away from God, then why is the demon possessing her? So far, the demon seems content to give Casey superpowers and make her masturbate with curling irons.
If nothing else, Fox’s The Exorcist is a perfect example of the current style of Hollywood storytelling. It attempts to create empathy for Kat by making her a lesbian; it gives obligatory nods to class warfare in the Father Tomas vs. the Catholic Church lunch scene (of course the French-speaking bishop thinks Tomas is on the right track because Europeans are more enlightened); and it casts organized religion in (almost) as negative light as a television show about Catholics can get away with.
Who’s summoning all the demons, anyway? A rogue exorcist? The Pope? Anything goes, it seems.
This episode was more focused than the 
Father Marcus says of the Bible, “Most of the words in here are man’s words, not God’s.” This gets to the heart of the problem with the show: they’re secularizing the source material. Which parts, exactly, are God’s words, then? And why didn’t those words work on the possessed homeless lady on the street? Which Biblical scholar in the production crew decided the difference between man’s and God’s words?
On the terrific website 
In 1986, a lunatic named David Young took the faculty and student body of 
