There is a long history of social-scientists using literature as foundational evidence for their ideas and theories. If you want proof of such a claim, go take a look at the now archaic Totem and Taboo or even the OG Communist Manifesto. For a more modern version, just crack open Things Hidden since the Foundation of the World. You’ll be inundated.
At first, this seems laughable. Literature? As scientific evidence? Aren’t most great works of literature fictional? How can something fictional possibly be used rigorously?
Alas, it cannot! Obviously, one should not use fictional literature as rigorous evidence in the sense of ‘providing explicit information about an event or occurrence.’ If I claim that Alice killed Bob, and then justify my claim by citing a classic Dostoevsky novel where Alice kills Bob (in this hypothetical world, such a novel exists), you’d rightly inform me of my idiocy.
As scholars of the humanities and social sciences love to point out, rigorous science isn’t everything. Speaking from experience, this is a hard pill to swallow. Despite the fact that extracting precise scientific value from literature is nearly impossible, literature does have an interesting characteristic that allows for the embedding and subsequent extraction of useful information.
The characteristic of which I speak stems from the fact that literature is a subset of books, and books are Lindy. This means that any literature in the zeitgeist of the current day has survived the cumulative literary scrutiny of all human beings who lived between the publishing of such literature and now. This is an extremely difficult thing to do, which is why we see such a tiny number of pieces of older literature that have maintained their high graces in the cultural tastes of every era since they were published.
It’s also a useful trait! We can (roughly) deduce that old literature which has been in the zeitgeist for a long time encodes something deep about the preferences of human beings. I suspect this is the utility that people like Freud, Marx, and Girard saw in it. Analyzing literature is then akin to analyzing a highly-agreed-upon version of human values and preferences, something which is extremely valuable if you’re studying human values and preferences.
The next time that you encounter a claim that makes use of literature for evidence, do your best to evaluate it while keeping the above characteristic in mind. Social science often seems like useless and obscurantist gobbledegook, but some of the people that operate in this space know what they’re doing, and their ideas are good.