The Copernican principle is the philosophical statement that no "special" observers should be proposed. The term originated in the paradigm shift from the Ptolemaic model of the heavens, which placed Earth at the center of the Solar system because it appears that everything revolved around Earth. Nicolaus Copernicus demonstrated that Earth is not, in fact, in the center of the system and the motion of the heavens can be explained without assuming that we are observing from a special position.
See also: anthropic principle, cosmological principle, mediocrity principle, Doomsday argument