One day, when he was contributing to the Tax and Welfare Working Group, economist Gareth Morgan made an off-the-cuff remark that the solution to all of New Zealand's tax and welfare woes lay in abolishing the present welfare system and radically overhauling the tax system. He called this idea the big kahuna.
The Big Kahuna takes as its base assumption that we don't, as a society, accept that huge differences in income are acceptable and that we therefore choose to redistribute wealth. While they are generally regarded as separate, the tax and welfare systems are fundamentally both methods of doing just that - redistributing income from those who have plenty to those who don't.
In a nutshell, The Big Kahuna seeks to show that if the job of redistributing wealth and income is worth doing, it's worth doing properly, so that the resulting system is fair to all, rich and poor alike.