Its weak form is a tautological statement that the universe must be compatible with our knowledge that carbon-based life exists.
One use of it has been to suggest that a large axion decay constant, naively ruled out due to its prediction of an overabundance of dark matter, is allowed due to a highly tuned initial angle. Hoyle's argument for the existence of a particular resonance of carbon-12 is often considered a use of this principle. In cosmology, it is the subject of a book by Barrow and Tipler. Its name was coined by Brandon Carter, and one prominent use is Stephen Weinberg's 1987 prediction of a small cosmological constant on the basis of galaxy formation. Its weak form is a tautological statement that the universe must be compatible with our knowledge that carbon-based life exists. For 10 points, what is this controversial principle which in one strong form relies on an ensemble of universes in which we live in a rare habitable region?
One use of it has been to suggest that a large axion decay constant, naively ruled out due to its prediction of an overabundance of dark matter, is allowed due to a highly tuned initial angle.
the anthropic principle