The 2005 election has been the most significant in decades. Taxation has become a defining issue and should remain so. The prosperity as well as the decline of nations has nearly always been related to taxation.

How a government taxes its people is a primary moral issue with profound social consequences. It influences how people behave and the choices they make.

Tax has become a prevailing issue for Helen Clark in New Zealand and Angela Merkel in Germany. The connection between the two countries is compelling. Clark has followed the European model of Social Democracy led by Gerhard Schroeder. Merkel's liberal economic policies and more conservative understanding of European culture is resembled more closely by the National Party.

Arguments around the value of a flat tax (Will Hutton, Herald, September 20) lie in the confusion over social justice or equity with justice. It is this confusion that lies at the heart of the present conflict between Angela Merkel, Gerhard Schroeder and the German people. And, indeed, in the present debate here.

One famous Scotsman, Adam Smith, said taxes paid to the state should be in proportion to the revenue citizens enjoy under the protection of the state. A famous Irishman, Edmund Burke, was a little more poetic, "To tax and to please, no more than to love and be with, is not given to men."

Tax is about justice and human nature before it is about wealth redistribution.

In Germany and New Zealand there is an appetite for change. But there is also a suspicion in both countries of any tax policy that looks like it will erode the prevailing ideology of social democracy which remains pervasive in both nations.

In spite of what Hutton says, a flat tax is not a new economic idea seized by that bete noir of the left, the US neocon. And neither are the British Tories nor Germany's new Chancellor Merkel "batty" for considering it. A flat income tax is a just and aesthetically proportional tax. It is not symptomatic of "a feeding frenzy of the rich".

But Hutton is right on one thing: you can't be wrong all the time; "economic nonsense will out, society does matter, and the rich do have obligations". He is right, but for the wrong reasons.

Social justice is vaguely associated with compassion and that vagueness seems indispensable. But as soon as we try to define social justice we run into embarrassing intellectual problems. It is really an instrument of ideological intimidation in order to gain the power of legal coercion. Consequently it underpins much of our thinking about taxation.

The fuzziness around social justice and its connection to taxation is what creates suspicion of the justice implicit in a flat tax. The mantle of justice is frequently applied to a social or political system of wealth redistribution which looks like compassion in action, when really the focus is not on virtue but on power.

The real battle is about the relationship between the individual and the state. More tax, bigger state, more bureaucracy, more law and less freedom. It is this captive mindset that makes people timid when confronted with greater personal responsibility.

The concepts of social justice and personal responsibility do not sit well together. It is this tension that arouses suspicion in any consideration of a flat tax. But the responsibility of individuals is the cement for the principle of ordered association so essential in a democracy.

The proponents of social justice who typically oppose flatter income-tax structures, often presuppose that people are guided by specific external directions rather than internalised personal rules of conduct. No individual can be held responsible.

It is the function of "social justice" to blame the system, to blame the oppressors who must be controlled by a new benign and inclusive state. In a command economy individuals are told what to do, so it is always possible to blame those in charge and hold them responsible.

Nothing will destroy an ordered society more, and erode the responsibility for others that each citizen should have, than a government that becomes monolithic in order to supply all our needs, when these can only be provided by the common effort of many and their wealth.

Until tax is examined in terms of justice, and not fuzzy social justice, such order remains fragile.

* Bruce Logan is director of the Maxim Institute.