## The Need for a Road Map in General Relativity

We have seen that the same formulas may have entirely different meanings and the same same physical phenomena may be explained in many ways. Two such examples are the general relativistic calculation of the deflection of light and the advance of the perihelion of Mercury. Both these phenomena were known before the advent of general relativity, and even the numerical gap in the advance of the perihelion was known, but not to the degree it is known today.