The principle of mediocrity is the notion that our evolution (biological, cultural, and technological) and our surroundings, including the Earth and the Sun, are typical rather than exceptional. It is often invoked, together with two other principles – the principle of plenitude and the principle of uniformity – to support the claim that life and intelligence occur commonly throughout the Universe. It is also an implicit assumption in SETI that other beings exist who wish to communicate and are sufficiently technologically compatible with us to make communication possible. The principle of mediocrity remains largely a matter of opinion but has been bolstered by the discovery of exoplanets and that certain organic chemicals, such as amino acids, occur commonly throughout space.