Is it possible to have a non-emotional debate about abortion? Mehdi Hasan fears not. The debate, he says, has become one of a clash of incommensurable ideas: the right to life of the unborn baby versus a woman's right to choose.

Framing the debate this way, however, misses at least five things. I mean:

1. How should we describe the abortion decision? Is it the termination of a potential birth, or merely the postponement of one?

Often, a woman has an abortion because she just doesn't feel emotionally or financially ready for the responsbility of being a mother. This is why abortion rates are three times (pdf) higher for under-18s than they are for 30-34 year-olds. A "woman's right to choose", then, is often not just a matter of choosing whether a foetus lives or dies. It is a matter of choosing whether to have a child in 2012 or, say, 2017.

2. If an abortion is the postponement of a birth, the question ceases to be: "does a foetus have a right to life?" and becomes: does a foetus have a right to life at the expense of a person yet to be conceived?

Put this way, we can answer Mehdi's question: "Who is weaker or more vulnerable than the unborn child?" The answer is: the unconceived one.

Two answers here are impermissible. One is that a foetus might be viable outside the womb. This fails because, as Owen Barder has said, rights cannot be contingent upon medical technology. The other is the argument from religion; this fails because it means nothing to non-believers.

This drags us into the question of the moral status of yet-to-be conceived persons and the non-identity problem. These are tricky issues, but very few people think we should be unconcerned about future, unconceived, people; worries about government debt or climate change are just nonsense if we take this view.

3. If an abortion is a postponement of birth, and so doesn't affect the size of the future population, doesn't utilitarianism argue for allowing abortion?

The argument here is that a child will have the best possible life, the better its upbringing, and if women can choose when to have a child, they are more likely to do so at a time that maximizes the quality of that upbringing.

Put this way, the argument for giving women a "right to choose" can be based not (just) upon self-ownership, but upon the idea that they are local experts best able to assess the well-being of future persons.

4.What if abortion is not a mere postponement of birth, but a way of restricting the size of the future population? You might argue on utilitarian grounds that this means abortion is a bad thing, as it prevents people being born whose lives would be worth living. Or you might argue that such reasoning leads to the repugnant conclusion.

5. Externalities matter. One could argue that banning abortion imposes a negative externality onto others. This is because in forcing women to have children they'll resent and bring up badly, we'll end up with a larger number of young people predisposed to crime. Granted, the claim that legalized abortion was responsible for the drop in crime in the US (pdf) and UK is econometrically (pdf) contested. But to me, it is intuitively plausible.

I don't say all this to take a stand on abortion; none of you should give a damn about my opinion. I do so merely to point out that there is more at issue here than a clash between a "right to life" and a "right to choose".