Gaia theory (or The Gaia Hypothesis) refers to several ideas; the most common include the following:
- Life on Earth significantly affect the climate, and can make radical changes to the environment (undeniably true)
- Established life on Earth acts to correct changes in overall climate, effectively displaying self-organization (arguable, but disputed)
- Life on Earth is, in a way, a single organism (possibly true, but of questionable relevance)
Probably the most useful aspect of Gaia theory is its value as a thought-experiment to explain to an unsophisticated audience how negative feedback might affect the Earth's climate; it is not a theory in the scientific sense. Any argument for a particular climatic outcome based on Gaia theory would be somewhat like trying to diagnose an illness after carefully studying the game "Operation".