Consider a football game. There are two extremes as to how it can be conducted. At one end of the scale, the outcome is set in advance by the organisers. The game is “fixed” for, let’s say, Collingwood to win, and all the rules, scoring, and umpiring decisions are tailored to achieve that outcome.

At the other extreme, there are no rules at all. Players attack one another with clubs or automatic weapons; boundaries and time limits are ignored; there are no umpires to interfere. Instead of absolute predictability, absolute chaos.

We would be incredulous if told that we had to choose between these two ways of playing football. Yet this is effectively the “choice” we are being offered when it comes to population policy. Everyone in the debate seems to assume that having a policy at all means targetting a particular outcome — a particular size for Australia’s future population.

In sport we have no difficulty finding a third option, the one we actually follow. We have the game played according to rules, which don’t try to predetermine the result but are supposed to embody our standards of fairness and our idea of what the game is about.

Of course, rules help determine results. Particular rules may favor some teams and disadvantage others; if we find that results are badly skewed one way — if one team wins all its games for years on end, for example — it suggests there’s something wrong with the rules. But playing the game by rules is nonetheless quite different from trying to fix the outcome in advance. That’s why sportspeople are taught that playing fairly and in accordance with the rules is more important than winning or losing.

A more serious example is the criminal justice system. Instead of setting out to ensure that a certain percentage of defendants are found guilty, we conduct criminal trials according to a set of rules that are designed to ensure fairness. The proportion of convictions that result is only one measure among several of how well those rules are working.

So while Australia’s total population is a matter of legitimate concern, so are many other things — its distribution, its skill composition, its age and gender profile. To target each independently in advance is a recipe for policy overload, not to mention endless political controversy. More important is for the rules of population policy to be fair.

What should those rules be? I would suggest two things, although they’re both aspects of the same idea of neutrality. First, a presumption in favor of free movement of people: that anyone who wishes to come to Australia, and meets certain objective criteria of fitness, should be allowed to do so. Second, that there should be no artificial incentives or disincentives for natural increase: people should not be discriminated against according to whether or not they choose to have children.

These are ideals, and a lot more work is necessary to translate them into practical policy. And of course they will be controversial. But surely no more controversial than trying to pick a number to represent Australia’s future population, and then work out how to achieve it.