Gaia philosophy

Gaia philosophy (named after Gaia, Greek goddess of the Earth) is a broadly inclusive term for related concepts that living organisms on a planet will affect the nature of their environment in order to make the environment more suitable for life. This set of hypotheses holds that all organisms on a life-giving planet regulate the biosphere in such a way as to promote its habitability. Gaia concept draws a connection between the survivability of a species (hence its evolutionary course) and its usefulness to the survival of other species.
While there were a number of precursors to Gaia hypothesis, the first scientific form of this idea was proposed as the Gaia hypothesis by James Lovelock, a UK chemist, in 1970. The Gaia hypothesis deals with the concept of biological homeostasis, and claims the resident life forms of a host planet coupled with their environment have acted and act like a single, self-regulating system. This system includes the near-surface rocks, the soil, and the atmosphere. Today many scientists consider such ideas to be unsupported by, or at odds with, the available evidence (see Gaia hypothesis criticism). These theories are however significant in green politics.
Predecessors to the Gaia theory.
There are some mystical, scientific and religious predecessors to the Gaia philosophy, which had a Gaia-like conceptual basis. Many religious mythologies had a view of Earth as being a whole that is greater than the sum of its parts (e.g. some Native American religions and various forms of shamanism).
Lewis Thomas believed that Earth should be viewed as a single cell; he derived this view from Johannes Kepler's view of Earth as a single round organism.
Isaac Newton wrote of the earth, "Thus this Earth resembles a great animall or rather inanimate vegetable, draws in æthereall breath for its dayly refreshment & vitall ferment & transpires again with gross exhalations, And according to the condition of all other things living ought to have its times of beginning youth old age & perishing."
Pierre Teilhard de Chardin, a paleontologist and geologist, believed that evolution unfolded from cell to organism to planet to solar system and ultimately the whole universe, as we humans see it from our limited perspective. Teilhard later influenced Thomas Berry and many Catholic humanist thinkers of the 20th century.
Buckminster Fuller is generally credited with making the idea respectable in Western scientific circles in the 20th century. Building to some degree on his observations and artifacts, e.g. the Dymaxion map of the Earth he created, others began to ask if there was a way to make the Gaia theory scientifically sound.
In 1931, L.G.M. Baas Becking delivered an inaugural lecture about Gaia in the sense of life and earth. 
Oberon Zell-Ravenheart in 1970 in an article in "Green Egg" Magazine, independently articulated the Gaia Thesis.
Many believe that these ideas cannot be considered scientific hypotheses; by definition a scientific hypothesis must make testable predictions. As the above claims are not currently testable, they are outside the bounds of current science. This does not mean that these ideas are not theoretically testable. As one can postulate tests that could be applied, given enough time and space, then these ideas should be seen as scientific hypotheses.
These are conjectures and perhaps can only be considered as social and maybe political philosophy; they may have implications for theology, or "thealogy" as Zell-Ravenheart and Isaac Bonewits put it.
Range of views.
According to James Kirchner there is a spectrum of Gaia hypotheses, ranging from the undeniable to radical. At one end is the undeniable statement that the organisms on the Earth have radically altered its composition. A stronger position is that the Earth's biosphere effectively acts as if it is a self-organizing system which works in such a way as to keep its systems in some kind of equilibrium that is conducive to life. Today many scientists consider that such a view (and any stronger views) are unlikely to be correct. An even stronger claim is that all lifeforms are part of a single planetary being, called Gaia. In this view, the atmosphere, the seas, the terrestrial crust would be the result of interventions carried out by Gaia, through the coevolving diversity of living organisms.
The most extreme form of Gaia theory is that the entire Earth is a single unified organism with a highly intelligent mind that arose as an emergent property of the whole biosphere. In this view, the Earth's biosphere is "consciously" manipulating the climate in order to make conditions more conducive to life. Scientists contend that there is no evidence at all to support this last point of view, and it has come about because many people do not understand the concept of homeostasis. Many non-scientists instinctively and incorrectly see homeostasis as a process that requires conscious control 
The more speculative versions of Gaia, including versions in which it is believed that the Earth is actually conscious, sentient, and highly intelligent, are usually considered outside the bounds of what is usually considered science.
Gaia in biology and science.
Buckminster Fuller has been credited as the first to incorporate scientific ideas into a Gaia theory, which he did with his Dymaxion map of the Earth.
The first scientifically rigorous theory was the Gaia hypothesis by James Lovelock, a UK chemist.
A variant of this hypothesis was developed by Lynn Margulis, a microbiologist, in 1979.
Her version is sometimes called the "Gaia Theory" (note uppercase-T). Her model is more limited in scope than the one that Lovelock proposed.
Whether this sort of system is present on Earth is still open to debate. Some relatively simple homeostatic mechanisms are generally accepted. For example, when atmospheric carbon dioxide levels rise, plants are able to grow better and thus remove more carbon dioxide from the atmosphere. Other biological effects and feedbacks exist, but the extent to which these mechanisms have stabilized and modified the Earth's overall climate is largely not known.
The Gaia hypothesis is sometimes viewed from significantly different philosophical perspectives. Some environmentalists view it as an almost conscious process, in which the Earth's ecosystem is literally viewed as a single unified organism. Some evolutionary biologists, on the other hand, view it as an undirected emergent property of the ecosystem: as each individual species pursues its own self-interest, their combined actions tend to have counterbalancing effects on environmental change. Proponents of this view sometimes point to examples of life's actions in the past that have resulted in dramatic change rather than stable equilibrium, such as the conversion of the Earth's atmosphere from a reducing environment to an oxygen-rich one.
Depending on how strongly the case is stated, the hypothesis conflicts with mainstream neo-Darwinism. Most biologists would accept Daisyworld-style homeostasis as possible, but would certainly not accept the idea that this equates to the whole biosphere acting as one organism.
A very small number of scientists, and a much larger number of environmental activists, claim that Earth's biosphere is "consciously" manipulating the climate in order to make conditions more conducive to life. Scientists contend that there is no evidence to support this belief.
Gaia in the social sciences.
A social science view of Gaia theory is the role of humans as a keystone species who may be able to accomplish global homeostasis. Whilst a few social scientists who draw inspiration from 'organic' views of society have embraced Gaia philosophy as a way to explain the human-nature interconnections, most professional social scientists are more involved in reflecting upon the way Gaia philosophy is used and engaged with within sub-sections of society. Alan Marshall, in the Department of Social Sciences at Mahidol University, for example, reflects upon the way Gaia philosophy has been used and advocated by environmentalists, spiritualists, managers, economists, and scientists and engineers (see The Unity of Nature, 2002, Imperial College Press: London and Singapore). Social Scientists themselves in the 1960s gave up on systems ideas of society since they were interpreted as supporting conservatism and traditionalism.
Gaia in politics.
Some radical political environmentalists who accept some form of the Gaia theory call themselves Gaians. They actively seek to restore the Earth's homeostasis — whenever they see it out of balance, e.g. to prevent manmade climate change, primate extinction, or rainforest loss. In effect, they seek to cooperate to become the "system consciously manipulating to make conditions more conducive to life". Such activity defines the homeostasis, but for leverage it relies on deep investigation of the homeorhetic balances, if only to find places to intervene in a system which is changing in undesirable ways.
Tony Bondhus brings up the point in his book, "Society of Conceivia", that if Gaia is alive, then societies are living things as well. This suggests that our understanding of Gaia can be used to create a better society and to design a better political system.
Other intellectuals in the environmental movement, like Edward Goldsmith, have used Gaia in the completely opposite way; to stake a claim about how Gaia's focus on natural balance and resistance and resilience, should be emulated to design a conservative political system (as explored in Alan Marshall's 2002 book "The Unity of Nature", (Imperial College Press: London).
Gaians do not passively ask "what is going on", but rather, "what to do next", e.g. in terraforming or climate engineering or even on a small scale, such as gardening. Changes can be planned, agreed upon by many people, being very deliberate, as in urban ecology and especially industrial ecology. "See arcology for more on this 'active' view."
Gaians argue that it is a human duty to act as such - committing themselves in particular to the Precautionary Principle. Such views began to influence the Green Parties, Greenpeace, and a few more radical wings of the environmental movement such as the Gaia Liberation Front and the Earth Liberation Front. These views dominate some such groups, e.g. the Bioneers. Some refer to this political activity as a separate and radical branch of the ecology movement, one that takes the axioms of the science of ecology in general, and Gaia theory in particular, and raises them to a kind of theory of personal conduct or moral code.
Gaia in religion.
Hinduism has many tenets of Nature worship and preservation. The ecologist and theologian Anne Primavesi is the author of two books dealing with the Gaia hypothesis and theology.
Rosemary Radford Ruether, the American feminist scholar and theologian, wrote a book called "Gaia and God: An Ecofeminist Theology of Earth Healing".
A book edited by Allan Hunt Badiner called Dharma Gaia explores the ground where Buddhism and ecology meet through writings by the Dalai Lama, Gary Snyder, Thich Nhat Hanh, Allen Ginsberg, Joanna Macy, Robert Aitken, and 25 other Buddhists and ecologists.
Many new age authors have written books which mix New Age teachings with Gaia philosophy. This is known as New Age Gaian. Often referred to as Gaianism, or the Gaian Religion, this spiritual aspect of the philosophy is very broad and inclusive, making it adaptable to other religions: Taoism, Neo-Paganism, Pantheism, Judeo-Christian Religions, and many others.
Semantic debate.
The question of "what is an organism", and at what scale is it rational to speak about organisms vs. biospheres, gives rise to a semantic debate. We are all ecologies in the sense that our (human) bodies contain gut bacteria, parasite species, etc., and to them our body is not organism but rather more of a microclimate or biome. Applying that thinking to whole planets:
The argument is that these symbiotic organisms, being unable to survive apart from each other and their climate and local conditions, form an organism in their own right, under a wider conception of the term organism than is conventionally used. It is a matter for often heated debate whether this is a valid usage of the term, but ultimately it appears to be a semantic dispute. In this sense of the word organism, it is argued under the theory that the entire biomass of the Earth is a single organism (as Johannes Kepler thought).
Unfortunately, many supporters of the various Gaia theories do not state exactly where they sit on this spectrum; this makes discussion and criticism difficult.
Much effort on behalf of those analyzing the theory currently is an attempt to clarify what these different hypotheses are, and whether they are proposals to 'test' or 'manipulate' outcomes. Both Lovelock's and Margulis's understanding of Gaia are considered scientific hypotheses, and like all scientific theories are constantly put to the test.
More speculative versions of Gaia, including all versions in which it is held that the Earth is actually conscious, are currently held to be outside the bounds of science, and are not supported by either Lovelock or Margulis.
Gaian reproduction.
One of the most problematic issues with referring to Gaia as an organism is its apparent failure to meet the biological criterion of being able to reproduce. Richard Dawkins has asserted that the planet is not the offspring of any parents and is unable to reproduce.