principle of plenitude
The principle of plenitude is the name given by historian Arthur O. Lovejoy1 to the philosophical doctrine according to which the nature of God, or the fecundity of nature, is such that every situation that can be realized will be realized. Throughout history, it has been a central tenet of those arguing in favor of pluralism. First employed by supporters of atomism, including Epicurus and Lucretius, it was used in a theological sense to support the case for numerous inhabited worlds by Nicholas of Cusa and by others following the Copernican Revolution. In a more restrained way, it is now espoused by many researchers involved in astrobiology and SETI who contend that wherever conditions are not opposed to the development of life, life will be likely to appear. According to Carl Sagan:
The available evidence strongly suggests that the origins of life should occur given the initial conditions and a billion years of evolutionary time. The origin of life on suitable planets seems built into the chemistry of the universe.
1. Lovejoy, Arthur O. The Great Chain of Being. Cambridge, Mass.: Harvard University Press (1962).