Why do we love Back to the Future, the 1985 Michael J. Fox vehicle that forever linked the DeLorean DMC-12 with time travel in the popular imagination? Is it the drum-tight writing, thick with callbacks and historical in-jokes? Is it the way the film still resonates, a quarter century later, offering lessons and metaphors suited to our times? Is it Marty McFly's brain-melting guitar solo that mashes up 30 years of rock 'n' roll idioms? Is it Christopher Lloyd's hair?

Well, yes, doubtless it is all of these things. But it's also--at least according to Slate--the way the film takes the squirmy subject of mother-son incest and makes it fun. Cuddly, even.

Juliet Lapidos explains:

Incest is absolutely central to the plot. What's genius about Back to the Future, however, is that it still manages to be unfailingly PG. It's a film about having sex with your family that's family-friendly ... Lorraine develops a crush on her son, and now Marty must figure out not only how to get back to 1985 but how to transfer his mother's affections from himself over to his father. Otherwise, he and his siblings will never be born. This seems icky.

But Lapidos goes on to note that "Lorraine's infatuation never feels un-Disney... Back to the Future presents mother-son attraction not as a perversion, but as one of those things that just happens and kinda makes sense, if you think about it, since in this reality mother and son are the same age." It helps that Marty's discomfort mirrors the viewer's own: "Marty doesn't want to replace his father; on the contrary, he spends much of the movie trying to unite his parents."

Which leads to the movie's other big Freudian conceit: that guitar solo at the Enchantment Under the Sea dance. "After George kisses Lorraine, Marty's so ecstatic that he leads Marvin Berry et al. in a rousing rendition of Johnny B. Goode, which culminates in a rather bawdy, suggestive guitar solo. His parents' (symbolic) orgasm leads to his own. Otherwise put: Marty (symbolically) masturbates to his parents (symbolically) having sex."

Whether or not you agree with Lapidos's reading, you have to admit it's a mofo of an argument.