A city's health is dependent upon that of the public realm

The third rationale for publicly provided social infrastructure - community solidarity - is grounded in one of the fundamental tenets of liberal democracy: the need for a public realm that supports and nourishes civic values and obligations.

Indeed, this may be the most important reason for a public realm. Liberal democracy is deeply premised on the need for a civic sphere outside the immediate reach of private interests (markets, families, and so on) where the basic values and obligations of citizenship are learnt and upheld.

Public spheres are where all citizens - irrespective of socioeconomic or cultural background - are welcome and where the rules and norms that are fundamental to democracy are cherished. Importantly, the public realm is a sort of "civic school" which newcomers (the young, migrants) and outsiders (such as gated communities) can experience and learn key democratic values, such as tolerance, equality of treatment and mutual obligation.

The great project of building Canberra - supported by all sides of politics, especially the Menzies Government - was a specific instance of how a growing and flourishing public domain assists the broader development and strengthening of liberal democracy.

It is no exaggeration to say that the health of a democratic body - a city, a nation - is reflected in, and dependent upon, the health of the public realm.

And so, will the proposal to allow the private sector to provide municipal social infrastructure harm Brisbane's public realm? The answer is surely yes, because the mixing of market and civic functions will blur the purpose of the public realm and send confusing signals to the citizenry about the fundamental democratic rules and values.

The market already has plenty of space - indeed, it now occupies more of our "lifeworlds" than ever before. A splintered public realm might well shatter the broader bases for our democracy.