5. Political will . There is always resistance to change, there are always interest groups – often rich and powerful withal – who will do whatever it takes to obstruct necessary improvement. In the era of the sanitary revolution, it was the owners of water companies, factories, and tenement housing who resisted most vigorously. Legislation and regulation are almost always necessary, and inevitably generate opposition. But when the other four features -- awareness, understanding, capability, and values – are in place, the political will to bring about reforms gathers momentum and usually succeeds eventually.