It is important that we make clear at this point what definition is and what can be attained by means of it. It seems frequently to be credited with a creative power; but all it accomplishes is that something is marked out in sharp relief and designated by a name. Just as the geographer does not create a sea when he draws boundary lines and says: the part of the ocean’s surface bounded by these lines I am going to call the Yellow Sea, so too the mathematician cannot really create anything by his defining.
—Gottlob Frege, The Basic Laws of Arithmetic , 1893