This week Joe West asks why screen sex is the ultimate taboo.

In western culture it is far more acceptable to see a film in which a child is stabbed with a sword (The Hunger Games, for example) than one which shows a penis stabbing a vagina. Even that sentence manages to fetishise the relationship between sex and violence and explode an image bomb inside your head for which I take only a fraction of the responsibility.

I don’t think that this general expunging of explicit sex from cinema is necessarily motivated by prudishness, gender politics or a general distaste for the sight of strangers’ turgid genitals slapping into one another. There are other, more practical reasons that it doesn’t appear on our screens outside of material which is primarily intended as pornography.

The first is due to the complexity of the sexual act itself, as opposed to the simplicity of a violent one. If all goes well, both parties should be alive after intercourse, which means that there is no narrative finality afforded by this plot point. Couples have to bonded by institutions like marriage, or linked through the creation of a child, because sex doesn’t resolve anything in movies, whether it is shown or not. A villain gasping his last, however, is pretty conclusive.

Secondly, no director ever asks an actor to literally perforate a kid using a katana. There are stunt doubles and special effects to bring the blood-letting to life. Of course stunt doubles do exist in the realm of the wanton, but their job requires the equivalent of an action movie stand-in really plunging to his death without a stack of boxes out of shot to break the fall.

Which brings us to the whirlwind of publicity surrounding 50 Shades of Grey and its suitability as material to inspire a mainstream movie. Porn star James Deen has been connected with the project, as have a number of other leading men whose bodies of work are not quite so X rated. And while I’m perfectly happy for directors to include sex, real or fake, if they feel that they can do so without reducing it to a gimmick, it seems pretty obvious that this particular adaptation is completely missing the point.

Movie sex is not primarily meant for real time self gratification, although it doubtlessly supplies this in spades to people who seek it once home releases are made available. Pornography, on the other hand, serves little other purpose. And as far as I understand it, 50 Shades of Grey is an erotic novel, leaning towards the pornographic, which should, if it’s doing its job, provide the reader with the motivation to knock one out.

Now, masturbation is awesome and healthy, but if you wrap up a pornographic film in mainstream trappings and attempt to release it in major cinema chains rather than straight to video, won’t you just end up frustrating audiences who’ve come to come, but can’t because to do so in a crowded Cineworld is a bit crude?

Also, it seems that the 50 Shades phenomenon has become so ubiquitous because it lacks the lurid seediness of male-oriented pornography, instead choosing a format which stimulates the imaginations of female readers and can, most importantly, be read on a Kindle; 2012’s brown paper bag. Taking this world, which exists in unique, fantastical form in the mind of each reader, and then transposing it into an inherently visual medium surely ignores the reason for the book’s success.

Ultimately, sex is excluded from films because it is actionable. Seeing people fuck makes audiences want to emulate it. There are those who would argue that the same is true of screen violence, although the alternative view is that action and danger are gratifyingly cathartic as viewers can live out fantasies vicariously through stars from the comfort of a cinema. Conveying the sensation of an orgasm, on the other hand, requires audience participation.