Or rather male-preference primogeniture, for that is the system used in the UK to determine the line of succession to the throne; anyway seems it's one of the things on Gordon Brown's mind at the moment. Not the imminent G20 conference, nor the state of the economy, the threat of deflation (or Islamic terrorism), the unprecedented size of the national debt or the fact that for the first time since New Labour came to power an auction of UK gilts was under-subscribed or even the worst fall in quarterly GDP since 1980. Nope, none of those things have priority, it's the possibility that at some point in the future Prince William's eldest child might be a girl that's the thing to be worried about! Does anyone else suspect this is something of a diversionary measure? Well yes, lots of people are saying just that, but that's no reason not to join in.
Of course you can argue that male preference primogeniture discriminates against women, and "the government is against all forms of discrimination", but this is where it starts to go wrong. The basic idea is to replace the male preference system with absolute primogeniture, that is the throne passes to the eldest child regardless of sex. So instead of sex discrimination, lets have age discrimination instead! This is why it looks like a measure designed to get the awfulness of the Brown premiership off the front pages for a bit, its a typical un-thought-through policy. If discrimination is the issue, then don't discriminate.
To use an analogy: imagine it isn't the throne, it's the position of CEO of a large and wealthy corporation. To appoint a new CEO the shareholders/board generally invite applicants and/or consider potential candidates, carry out an assessment then make a choice. Imagine instead that they have primogeniture like rules that lay out who the next CEO has to be, and for the sake of the analogy these rules state that the role has to go to the eldest male applicant. Actually the analogy makes more sense (as appointing the eldest applicant is clearly nonsense) if the rule is that it has to go to the first male applicant to apply - the analogy still works as it retains the element of timing. So, we have to appoint the first bloke who gets his CV through the door!
Now the female applicants all cry foul, saying this is discriminatory. OK we reply, you're right, it is, lets do what Gordon Brown proposes and replace the "first male applicant" rule with a "first applicant" rule. Fantastic, we no longer discriminate on grounds of sex, but if anything we've made the process more stupid not less; we certainly haven't made it more sensible by removing the element of sexual discrimination. And this is the thing, if you're against all forms of discrimination then replacing one with another is contradictory if not hypocritical.
The point of rules of inheritance is that otherwise someone actually has to make a decision. In many cases this is fine, but in the matter of thrones it has lead to wars in the past, so a clear set of rules is by no means a bad thing. You might argue that discriminatory rules can never be a good thing, but any such rule has to be discriminatory by its very nature and basing discrimination on age is no better than discrimination based on sex. So whats the alternative?
Well clearly one alternative would be to abolish the monarchy, but then you have the even worse position of a politician becoming head of state. Is there another way, well yes: an elective monarchy. It's still discriminatory, but now we discriminate on grounds of merit, and that can't be a bad thing surely.