Following on from this post, I'd like to ask what is wrong with libertarianism as a political philosophy? After all, liberty is a great quality, one that Greens have always valued, and do still value, most highly. Liberty is the focus of the Arab Spring, of revolutionary and anti-colonialist movements worldwide and throughout history. Liberty is good.
The problem comes when ideas, however valuable, are transformed into ideals, are set on a pedestal and mutate into a reference point with which the rest of reality must be compared.
The French Revolution set Liberty up alongside Equality and Fraternity. Sadly, modern libertarians seem to have no truck with equality and most show precious little fraternity with those who disagree with them.
Libertarianism itself is a broad church, stretching from penniless anarchists to dogmatic and uncritical supporters of free market capitalism. It is this latter category that are very much the opponents of all things ecological, in the forefront of denial that it is in any way necessary to care for our environment or society.
In that libertarianism is a form of individualism, it falls at the first biological hurdle, since homo "sapiens" is unquestionably a social animal, like the chimpanzee, not a solitary animal like the bear.
Next, there are certain physical constraints on human liberty.
First, there are ecological necessities: we are obliged to provide ourselves with water, food, shelter, energy, and waste disposal. Which means we have to work.
Second, we need security. No-one is free if they cannot go out of the house without being shot or mugged. That implies two levels of social ordering: first, a decent, solid, cooperative society. This in itself needs equality if it is to work well. Second, regrettably, it needs police, courts and a just penal system.
The same goes for our individual health requirements: a civilised nation needs a universal health insurance service that supports us when ill. Already we are on our way to creating a State - something that libertarians are allergic to.
Third, we need an ethic that stops us expressing our individuality in such a way that the freedom of others is infringed. For instance, we are not free to shout and sing at the tops of our voices in the streets at night, because this may infringe the freedom of others to sleep.
This ethical principle means that we are not free as a society to produce chemicals if there is sound evidence that the effect of these chemicals will be to compromise the freedom of our descendants to enjoy a secure and happy life.
It is at this last point that libertarians seem to trip up. It is an intrinsic weakness of individualistic philosophy that it has to apply an extension to the core belief to produce an ethic. The extension is called enlightened self-interest. It goes like this: if I behave kindly to others, others will behave kindly to me, and we will all be that much happier. There are I am sure many decent libertarians for whom enlightened self interest works like a charm. However, there are others who seem to have difficulty making this jump. If anything crosses their horizon that requires them to question their behaviour, the immediate response is to attack that thing as untrue. That is when libertarianism slides down into selfishness, and is one of the reasons that the most important debate of our century is between Greens and Libertarians.