's conditions, as the Earth is the only planet currently known to harbour life. The release of this image prompted the formulation of the proposition that the Earth was alive, and fostered acceptance of that proposition.]]

The Gaia hypothesis is an ecological hypothesis that proposes that living and nonliving parts of the earth are a complex interacting system that can be thought of as a single organism. Named after the Greek earth goddess, this hypothesis postulates that all living things have a regulatory effect on the Earth's environment that promotes life overall.

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 theories holds that all organisms on an extraterrestrial life giving planet regulate the biosphere to the benefit of the whole. The 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 theory, 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 homeostasis, and claims the resident life forms of a host planet coupled with their environment have acted and act as a single, self-regulating system. This system includes the near-surface rocks, the soil, and the atmosphere. While controversial at first, various forms of this idea have become accepted to some degree by many within the scientific community (See Amsterdam declaration on Global Change).

These theories are also very significant in green politics.