Previously, I posted about how philosophy or theory might be applied to film to explain how a particular concept might play out in reality. Applications to film could also be considered useful because of a sort of reverse-explanatory power at work here. By this I mean that showing the operation of a particular idea in a film might help to elucidate the idea itself.
So, we can read Freud and understand what he means by a neurosis, but his 'case studies' don't necessarily provide good examples of how these neuroses play out in reality - the case studies are selected for a reason, probably for their extremity (see the 'rat man' or 'wolf man' for good examples of these). If we take a film like Marnie (1964), on the other hand, we might have a more realistic depiction of how neurosis might play out.
In Hitchcock's Marnie, the main character, Marnie, lives as a crook in order to exist outside of your average social order of the time. In her case in particular, it seems she works as a crook in order to make enough money to support herself and her mother, while giving her the freedom to avoid marrying. In the end of the film, the male protagonist Mark Rutland performs an impromptu session of clinical-psychoanalysis by making Marnie remember repressed memories of her childhood - the source of her fear of men and the color red.
While the depiction of a man-hating woman who is 'set straight' through the use of psychoanalysis is a somewhat ridiculous issue (one that warrants more discussion), the example of how a neurosis operates for Freud is clear. We can look at Marnie as a fairly straightforward example of this, and in our application of psychoanalysis to this film the reverse-explanatory principle emerges. The irrational fears (neurosis) are the result of a repressed memory from childhood, and the understanding of this link provides the patient relief from the fears.
So yes, concepts may be applied to film in an attempt to understand the film, but this also initiates this reverse-explanatory mode of thinking where the film helps to define the concept itself. This seems useful to me, if only for the purposes of teaching, learning, or understanding.
And yes, I am really just saying that movies can help us understand ideas. But it is interesting, because Marnie was not created to be a didactic film - it wasn't created to teach us about psychoanalysis. But, as a cultural text that engages with these particular ideas, there is this didactic quality that emerges as a result of being a cultural construct.