Sustainability is not a number. It is a way of life. This is an inconvenient fact that much of the debate over Australia's population ignores.

Whether Australia's population stays at 22 million or grows to 35 or 40 million is an incidental statistic when what defines sustainability is not the number of people but the way they live. Right now, at 22 million, Australia has an 'unsustainable' population insofar as we are consuming faster than our natural resources can renew and polluting more than the environment can absorb.

Australians are the highest per-capita emitters of carbon pollution in the world, and as individuals we have the highest ecological footprints on Earth. Stabilising Australia's population right now, as some demand in the name of 'sustainability' will not alter this. In fact, much of the motivation for shutting the doors on immigration for example is to defend rather than challenge the Australian way of life as it currently exists. Many Australians mistakenly believe that if we stop growing, we can keep our big cars, big houses, and big bellies just the way they are. In the name of sustainability such people actually underestimate the unsustainable nature of their current lifestyle.

Furthermore, the obsession with reducing numbers ignores the other aspect of sustainability - that the change to a sustainable economy will demand huge investments in skills and labour and a tremendous amount of hard work. A growing Australia, with more people, younger people and more skills will be better equipped to make the change to sustainability than the contracting and declining nation demanded by the 'Small Australia' bandwagon.

As I argued previously, when looked at in global terms Australia's population is small and could stand to be a lot bigger. This is not an argument for unlimited or unplanned growth. Australia pays dearly to maintain a small population at First World living standards over vast distances and another ten million oil junkies stand to make the problem worse. Yet stopping population growth and reducing it to a sustainable number is not an option.

Jared Diamond's magical figure at which he wildly conjectured Australia's current lifestyle could be sustained was 8 million. It is a magical number because there is no practical way to reach it - and once there, it would not look at all sustainable. If we stopped all immigration and stopped reproducing right now (both things which are by themselves politically impossible to sustain), imagine how long it would take for enough people to die to reach 8 million - and finally imagine what the remaining 8 million would look like. What kind of a society would we be left with? If the answer is extinction, then the solution was not sustainable in the first place.

The German philosopher Hegel argued that history moves in a progression of theses and antitheses. Each 'stage' of human history contains within it the seeds of its overthrow and the next stage. Thus it must be that the next stage of human history must be contained within our current situation. Those who argue the world's population must be reduced right now are trying to leap outside of history rather than change its direction. There is no coincidence that their attitude is one of overwhelming defeatism and negativism towards the human species. Like Schopenhauer, they rage against the misery of life while nonetheless consuming it.

The Science fiction writer Isaac Asimov also looked at history in terms of momentum and mathematics. While his 'psychohistory' was a fantasy, there was within it a vital seed of truth. Human history is also driven by critical masses of movements, people and cascading events. To turn such a critical mass around would require in itself a critical mass of people, movements and events. The other element of Asimov's theory that stands repeating is that human nature is not something that changes much over time. We are not likely to change the course of history by trying to stand against an overwhelming tide or against human nature itself.

Both of these philosophical considerations lead us to one conclusion. The world's population, and that of Australia, will grow a lot more before it stabilises. Australia's economic growth is reliant on immigration and Australians will keep having families. People will demand high standards of living and the urbanisation of civilisation will continue. What we can do is look for the seeds of the next stage not outside of history, but in our current condition and trajectory. We need to find ways for the planet to sustain a population of 10 billion people, and for Australia to take its fair share in a sustainable way.

That means focusing not on the number, but on the way of life - and making changes that in themselves can be sustainable politically, socially and economically as well as ecologically.

As a growing, wealthy nation, Australia has the opportunity to make its population more sustainable through better planning of our cities and economy. Australian cities need to collect and recycle more water. Local communities need to grow more food and produce more of their own energy. Suburbs need to become more mixed use, higher density and housing a lot smaller and/or more productive. Our energy production and transportation methods need to be revolutionised. None of these are changes that require smaller populations - in fact retrofitting our cities let alone mitigating the effects of climate change such as rising sea levels and extreme weather events will require huge amounts of labour.

Rather than argue about the numbers of immigrants in this case, a far more important consideration is the composition of the immigration intake. Rather than focus their attention on the population numbers, those interested in sustainability should be asking how we plan and get to work making it happen. Pretty soon, the need for more hands, talent and energy, rather than less, will become evident.

When asked what he thought was a sustainable population, Tony Burke, Australia's new minister for sustainable population, evaded by saying he would 'like to see a situation where you can get a seat on a bus'. Perhaps a more ridiculous definition of sustainable population has never been verbalised - but it encapsulates the thinking of Small Australia perfectly. Its concern is to remain 'relaxed and comfortable' - chauffeur driven from door to door by the minister for sustainability if necessary. But perhaps sustainability actually means more standing room. Perhaps it means more buses, or less cars, or even less reliance on commuting in the first place. One thing that is certain is that a nation of empty buses will not last long.

Dr Aron Paul is a Melbourne-based writer and historian, and a postgraduate student in Environment and Planning at RMIT.