You can't have a great crime drama without a heavy dose of skepticism. The best TV detectives don't trust their hunches, they seek the truth. That requires massive quantities of doubt, so the detective (and viewers at home) doesn't just see the case the way he or she wants to see it.

There'd be no fun in watching the serious work of a detective who guesses right every time, but on a show like Medium, where the main character isn't just guessing, but employing an extra sense, it can be extremely easy for the viewer to simply slip into a default mode of trusting Allison Dubois completely. She is a psychic, after all, and episode after episode, she proves that her third eye is frequently right. So why is it then, that everyone - from the detectives Allison works with to her very own husband who loves her without question - has trouble swallowing her theories?

Skepticism is such an important part of watching Medium that doubting Allison almost becomes a character in the scene. It certainly plays a big enough role that Allison's surrounded by characters questioning her. According to series creator Glenn Gordon Caron, the skepticism Allison fields from her husband created a dynamic that was much more "relevant and interesting" than the simple fact of believing Allison or not, for the viewer. And to give the character Joe Dubois his due, many times on Medium, he is right to doubt his wife, and those tiny victories for the more logical-minded add dimension to the show. Caron said in an interview with the Archive of American Television:

I once heard marriage described as this deal, this compact that you make with another person. And how so many marriages ultimately fail is that while you’re married, you’re really sort of unknowingly renegotiating the deal. Because you change. Your experiences change you. And I believe what we’re watching [on Medium] is that negotiation going on. These two people clearly love each other, but what a love! … Here’s a guy who deals with the physical facts of the world, and here’s a woman who says, ‘I can’t talk to you now, there’s a Civil War soldier standing in the corner.’ … I find that relevant and interesting. It’s irrelevant to me whether it’s true [what she sees].

But while the skepticism in the show you sense from Joe was all part of the series creator's grand plan, the police presence of Detective Scanlon - the homicide detective Allison works with to solve cases - was actually ramped up on the show at the behest of the studio. Caron said that NBC requested a character like Scanlon be added to the show and despite Caron's skepticism that the show needed it, he said it actually “made a significant contribution to the show,” and that contribution, of course, was via Lee Scanlon's intense scrutiny of every claim Allison made.

The character of Lee Scanlon is introduced in the third episode of the series, "A Couple of Choices." In it, Allison is helping Scanlon solve a murder case that killed off a husband and wife. Before she arrives at the scene of the crime, Allison has a vision of a husband killing his wife in a murder suicide. When she suggests this, it touches a nerve for Scanlon, whose sister was killed by her husband in a murder suicide. It brings up questions: Is Allison's vision about Scanlon or the murder case? Scanlon doubts both, and from that episode on, whether due to this first impression or not, it's his character's job to squint at Allison's visions, seeking facts to back the psychic up.

But for many fans, the best manifestation of doubt when it comes to Dubois' visions is the District Attorney Manny Devalos, who in many ways acts as a voice of reason on the show. Unlike Scanlon, though, Devalos' doubts don't spring from a place of personal tragedy, but a dedication to presenting hard evidence in the courtroom. He's asking questions of Allison, not because he doesn't believe her, but because he knows that what she says is not enough to ensure justice is served. And that's why skepticism plays such a meaty role on Medium, because without doubt, every case is as open and shut as Allison's eyes when they fly open after a dream.