Today, three centuries after Newton, gravitation is still one of the enigmas of science. "It may well be the most fundamental and least understood of the interactions," says Robert H. Dicke. In all of the efforts that have been made to formulate a unified physical theory the big challenge has always been to bring gravitation within the theoretical framework. One of the most basic problems is to define the nature of the phenomenon. According to Einstein's general theory of relativity, the theory that is currently accepted (often with some reservations), gravitation is equivalent to a motion. This assertion implies that, while it has some of the characteristics of motion, it is actually not a motion. The objective of the present discussion is to examine the validity of this conclusion.