  Although many solar systems have been discovered, only one example of life is
known. Thus, terrestrial life represents merely one data point. Consequently,
extrapolating from terrestrial life to life elsewhere in the galaxy and beyond
is often seen as a limitation in the search for different forms of life.
Essentially, attempting to extrapolate from terrestrial life to life elsewhere
implies that terrestrial life is representative of all life, reflecting a
geocentric viewpoint. However, in accordance with the Copernican principle, the
opposite holds true. Asserting that terrestrial life must differ from other
forms of life in the universe is, in fact, the geocentric viewpoint. For if
life elsewhere is not like terrestrial life, then it is ipso facto different
life; more precisely, if terrestrial life does not represent general life, then
that life must represent special life, which the principle states it is not.
This study employs the Copernican principle as a probability assessment,
addressing critiques rooted in the implicit assumption of the existence of
different extraterrestrial forms of life. If various fundamental forms of life
indeed exist, then differences in the probabilities of their emergence can be
expected, forming a probability scale. This holds significance because it not
only allows for insights into the characteristics of the majority of life
elsewhere but also facilitates the establishment of boundaries for categories
of life as we do not know it. Thus, the Copernican-Darwinian principle provides
a valuable tool for astrobiology and the search for life in the galaxy and
beyond.
