John Knox stirs in his grave

It would become illegal to view this picture in Scotland. 

OK, let's start at the beginning. My party - the Scottish National Party - has introduced legislation making it an actual crime for girls under sixteen to have sex, and is now proposing to make it a crime to have images of 'rape'. These two matters are not distinct, they're linked. And to talk about why they're linked I want to start by agreeing that, yes, there are public policy issues here.

Young people are vulnerable to older people. When very young, they're very vulnerable; we teach young people to view adults as authority figures. Most of the time this is a good thing. But it means that young people are vulnerable to sexual advances from older people, sexual advances which they might have rejected from someone who did not have perceived authority. And, young people inevitably have less experience of sexuality than their elders; they don't have an appropriate repertoire with which to respond, and this too makes them vulnerable. So young people do have to be protected, and it's right that, as a society, we have rules which prevent adults predating sexually on children.

Similarly, rape is a serious matter. Rape, even if not violent, can have a devastating psychological effect on the victim. Again, issues of authority and of power are involved in rape. It's obviously right that, as a society, we should have rules which protect people (mostly women) from being forced into unwanted sex by others (mostly men).

So I'm not arguing for rape or for paedophilia. I'm arguing for open debate, clear thinking, honest statement of problems and issues. I'm arguing for free speech, and for freedom of artistic expression. Because it is at least partly through artistic expression that society develops its norms, and passes them on to rising generations. When Charles Dickens was concerned about the condition of children in Victorian London, he wrote novels about it. When Robert Burns wanted to express his opposition to slavery, he wrote poems about it. The novels and poems reached a far wider audience and ultimately affected political change far more effectively than dry factual accounts.

I'm not arguing that paedophilia is acceptable, but why is there considered to be a crime committed when two fifteen-year olds make love? Are they each supposed to be predating on one another? Are they each supposed to be predating on themselves? And does anyone - does anyone - believe that to have the police intervene in a relationship between two fifteen year olds is not going to be far more harmful to them than under-age sex ever is?

Yes, the state must provide young people with appropriate education, appropriate access to contraception and health-care and counselling. Yes, the state must protect young people from predatory adults. But criminalising the first tender development of sexuality? That is - literally - obscene.

And so we move onto the second issue. The government - my government - my party - proposes to make it illegal to possess images of

'Rape and other non-consensual penetrative sexual activity, whether violent or otherwise...'

Part of the legal fiction which gives rise to this sort of legislation is that somehow consent is simple, and that it's possible to tell from an image whether consent was given or not. But in practice, consent is not that simple. A person may consent to an act with a given partner, and not consent to the same act with the same partner a few days or hours or minutes later. The act is not different. One could not necessarily tell, looking at a photograph afterwards, which act was mutually consented to and which was not.

The need for sexuality, and the nexus between sexuality and aggression, is very deep in the human psyche, very close to the centre of who, and what, we are as people. We all have it, and it troubles many of us in one way or another. As playful creatures, many of us choose to explore these issues through play. Play in which there may be many layers of the granting or withholding of consent; games in which people may choose to consent to engage in forceful sex against their active protest.

And many people - perhaps, we don't know, very many people - find some degree of pain or fear enhances sexual pleasure. Consensual sexual activity can be extremely vigorous, can be extremely uncomfortable, and can involve implements designed and intended to cause pain. How many decent middle class homes in Scotland have a pair of handcuffs or a whip or flogger hidden at the back of a bedroom drawer? We don't know. I don't know and you don't know - because we're a sexually repressed nation. But the people who sell these things do a good trade, here in Scotland; I'd hazard a guess it's more than any of us would think.

This isn't to defend rape. It isn't to excuse rape. But rape is something that happens inside the head of the victim - consent is either given or withheld. Consent is not something a picture can show. Coercion does not need to involve violence; no matter how tender an image of sexuality, we cannot know by looking at it that one or both of the participants was not blackmailed into taking part. No matter how apparently violent an image of sexuality, we cannot know by looking at it that it has not been positively chosen and is not being actively enjoyed by all concerned.

There is a yet more serious issue beyond this. The present legislation is aimed at images; but will have a chilling effect on all art forms. If we cannot explore issues of sexuality, coercion, violence in narrative, in stories, in film, in other art, how are we to give our rising generations language in which to explore and understand what is appropriate and what is inappropriate? Repression does not stop things happening. People will continue to have sex. Some of that sex will continue be rough. But if we have outlawed discussion about what is, and what isn't, acceptable to us as a society, how are victims to know when it is appropriate to protest?