There are ... a number of general philosphical differences between Greens and Socialists that revolve around their similarities with each other and differences from Liberalism. Briefly stated, Liberalism rests on the ontological presupposition that isolated ``subjects'' (or thinking beings) exist in a universe consisting of an aggregate of discrete ``things'' (or objects) and the nature of their lives is learning to control things for their benefit. Socialism and ``Greenism'' rests on the presupposition that subjects or selves are not isolated discreteentities in a mechanical universe, but are instead part of a larger whole which constitutes them, and therefore the goal of their lives is, or should be, learning to understand the nature of that ``whole'' in order to bring themselves in line with its evolutionary unfolding or development.
The difference between Greens and Socialists is to be found in the ontological whole which they give a priori status to, i.e.the whole which they hold sacred and see as the source of their human potential. Liberals see only human bings as sacred and``whole'' (i.e.greater than the sum of their parts).
Socialists argue for the a priori status of society (i.e. society is also greater than the sum of its parts), Greens argue for the a priori status of nature (i.e. nature is greater than the sum of its parts) in all logical thought. In very simplistic terms Liberals give the individual the logical and moral status once given to God, Socialists give the same status to society, and Greens give it to nature. In this sense Green thinking is much more morally comprehensive since no subject is outside the realm of moral consideration because no subject is outside the realm of nature. In this sense there is no subject/object dichotomy since all issues must be understood as both subjective and objective. The terms are meaningless in isolation from each other.
As for concrete political differences between Green and Socialist thinkers there is one area in which ecological (or green) economists have clearly distinguished themselves from socialist economists. Socialist economists tend to argue for the ``socialization of economic externalities'' whereas ecological economists argue for the ``internalization of economic externalities.'' An externality is aneconomic cost or benefit (usually costs) which is not included in market prices. For instance, pollution is a real cost that isn't included in market prices so commodities produced in factories which dump wastes are in effect receiving a subsidy from the community. The people who suffer the health costs in the form of illness are the ones who pay that subsidy. This is the staus quo under Economic Liberalism (i.e. capitalism). The socialist response is to ``socialize'' the waste-costs, i.e. to create a government program to clean up the wastes or regulate their disposal and then pass the costs on to the society as a whole with no regard for who benefitted or was hurt by the unpaid waste-costs.
Liberal governments have traditionally adopted this ``socialist'' approach without calling for the end of capitalism. Full blown Socialists or Communists argue for end of capitalism through the nationalization of all major industry under the theory that if the state, which represents the people, owns the means of production then all benefits go to the people rather than capitalists. Money previously designated profit is now revenue for the state which supposedly means the money goes directly back to the workers who according to socialists are the ones who actually produced the wealth in the first place. We all know the practical problems of a full blown socialist state. It becomes too powerful and indifferent to the people. This solution to the problem of externalites (which incidently include crime and poverty not just pollution) has therefore come under greater criticism in recent decades.
The solution proposed by ecological economists is quite different. They argue that waste-costs (and unpaid or undervalued resource-costs, such as resources taken from forests, lakes, oceans, and the atmosphere) should be ``internalized'' rather than ``socialized.'' This means that unpaid waste-costs and resource-costs should not be picked up by the community as a whole (which do not all benefit in the same proportion) but rather these costs should be internalized into the market prices of commodities, so that only those who purchase a commodity or profit from its sale pay the costs associated with it. The result is that cleaner and less socially disruptive forms of production end up being cheaper rather than more expensive (their current status) than polluting and socially disruptive forms of production. In other words, things like fossil fuel generated power could not compete with solar generated power. The goal of cleaning up the environment is therefore accomplished without government clean up programs that treat all tax payers as if they benefit equally from the programs. In this sense, internalization produces an emphasis on personal responsibility rather than the tendency to blame ``society.'' The goal is a gradual tranformation of society rather than the call for a revolution of society.
This is an extemely crude overview of differences but it is where all the other more subtle differences begin. One other thing, if Greens (especially in the U.S.) in the grassroots movements wish to begin understanding how they are different from all the other ``isms'' they must throw out the idea that the differences can be understood in terms of the values they proclaim. The fact is that there is absolutely nothing unique or original about green values, what is unique is the hierarchical order thery profess for these values and more importantly the logical and practical arguments they use to defend and implement those values. I hope this is of some help to whoever asked this question ...
Sincerely,
Michael Christopher - PhD
University of Hawaii Hilo/Community College