Gaia philosophy
Gaia theory is a broadly inclusive name for a group of ideas that living organisms on a planet observe its biosphere and modify the nature of the planet to make it more suitable for life.
The first scientific form of this idea was proposed as the Gaia Hypothesis by James Lovelock, a U.K. chemist. While controversial at first, various forms of this idea became accepted to some degree by many within the scientific community. A variant of this hypothesis was developed by Lynn Margulis, a microbiologist, in 1979. Her model is more limited in scope than the one that Lovelock proposed.
Some years aftre this idea gained popularity, some within the environmentalist movemented integrated a non-scientific version of the Gaia hypothesis into their ideology; these people refer to themselves as Gaians. Some within left-wing politics and the Green party have also incorporated some variant of the Gaia hypothesis into their ideology.
For a more detailed discussion of scientific Gaia theories see Gaia theory in biology.
One theory at all scales
Long before Lovelock proposed his Gaia hypothesis, there had been a number of religious, mythological, and and philosophical ideas 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 Indian religions; some forms of Hasidic panentheism.
- To Lewis Thomas Earth can be most productively viewed as a single cell - a view that he derived from Johannes Kepler's view of Earth as a single round organism.
- To Teilhard de Chardin, a paleontologist and geologist, 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 - he later influenced Thomas Berry and many Catholic humanist thinkers of the 20th century.
- To Lee Smolin, a physicist, whole fecund universes could unfold from black hole implosions in this one - cosmology itself was determined ultimately by the same process of evolution, and parameters and constants that determined likelihood of life existing in new universes, were derived in some way from those of the "mother universe".
None of these ideas are are generally considered within the realm of science, as none make testable predictions. These are conjectures and perhaps can only be considered as social and maybe political philosophy, with implications for cosmology and theology.
It is not unusual for one model to be applied at many scales in science. In 20th ceuntury chemistry and astronomy, the "orbital" structure of electrons around neutrons, and planets around stars, were often compared.
Gaia in biology
Although Pierre Teilhard de Chardin was first to attempt to integrate the evolutionary biology view with theology, cosmology, and the duties of humans, 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 Gaia theory "respectable".
The first such attempt was the Gaia Hypothesis by James Lovelock, a U.K. chemist. While controversial at first, various forms of this idea became accepted to some degree by many within the scientific community. A variant of this hypothesis was developed by Lynn Margulis, discussed at Gaia Theory.
Lovelock's Gaia hypothesis was that the biomass modifies the conditions on the planet to make conditions on the planet more hospitable - the Gaia Hypothesis proper defined this "hospitality" as a full homeostasis.
Margulis's Gaia Theory loosened to claim only that the hospitality is temporary and homeorhetic. A system in homeostasis tends to move towards constant values for its parameters, whereas a system in homeorhesis will always exhibit similar dynamic behavior, without necessarily converging to a constant state - nor any "friendly state that would favour any existing organisms. There is very strong evidence that plants are selected for the microclimate effects which they can have locally to themselves, and good evidence that these patterns also exist on some wider scales, with symbiotic relationships existing for larger scale climate modification. There is also very strong evidence that mass extinction occurs when the conditions on a planet move to a new homeorhetic balance, unfriendly to existing organisms.
Diversity of hypotheses
Gaia theory remains a spectrum of hypotheses, from undeniable to radical. At one end is the undeniable statement that the organisms on the Earth have radically altered its composition. In this view, 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. Biologists usually view this activity 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. To some this leads directly to controversial conclusions:
There are planet-specific regularities in human cognition of our biosphere and universe. Without a way to consult with non-humans it is difficult to say exactly what they are, but, it is clear that if we grew up on a darker or louder or heavier or more oxygen-poor planet we would have stronger vision or weaker hearing or stronger legs or stronger lungs, and that this would affect our evolution and thus our view of our planet and universe in some unclear way. The Anthropic Principle in physics is an exploration of the ways in which our history as humans constrains what we see and care about in the universe: Eugene Wigner, Stephen Hawking and other physicists were prominent in raising these issues as part of the problem of cosmology.
Some environmentalists view the ecology and the ecology-viewing sentient organism as evolving together in an almost conscious process, in which the Earth's ecosystem is literally viewed as a single unified organism with the role of humans for instance to comprehend and integrate with ecology for ther own comfort. In many ways, this is a religious point of view, and that is most obvious in the views of Teilhard de Chardin and Thomas Berry who view Earth as a super-organism, in effect as an agent of God.
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 at all to support this point of view, and it has come about because many people do not understand the concept of homeostasis. Non-scientists instinctively see homeostasis as an activity that requires conscious control, although this is not so. This leads to some confusion on both sides, and claims of mysticism and scientism by some adherents.
Social science view
A social science view of Gaia theory is the role of humans as a keystone species. If they act to prevent climate change, primate extinction, etc., then they might make a homeostasis with their own cognition.
Some political environmentalists who accept some form of the Gaia theory call themselves Gaians. They 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.
Semantic debate
The question of "what is an organism" and at what scale is it rational to speak about organisms vs. biospheres, give 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 mre 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).
Lack of clarity
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 valid scientific theories, and are now a part of biology proper. 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. The views of self-proclaimed political Gaians are in this category.
Some Gaians appear to be developing a new theory, fusing conclusions from science and politics, that would be a protoscience of human ecology that includes humans as the keystone species deliberately maintaining the balances of the entire biosphere. They 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 other more radical wings of the environmental movement and 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.