principle of uniformity
The principle of uniformity is the assertion that the laws of nature discovered on Earth apply throughout the rest of the Universe. From this it is a reasonable, though not inevitable, conclusion that the same physical, chemical, and biological processes that gave rise to terrestrial life could also produce life elsewhere. The principle of uniformity is a fundamental tenet of science. Together with two other basic beliefs – the principle of mediocrity and the principle of plenitude – it used by most SETI proponents to argue that life and intelligence are not uncommon throughout space.