This is a hard question indeed. Einstein's theory shows that a very massive body will alter the space-time around it. The space-time has 4 dimensions: one time dimension and three space dimensions. I don't think he said that the gravitational force changes the direction of light. Gravitational force is an effect of the space-time as well. Thus both traversal of light and gravitational force are changed due to the massive body. But I might be wrong here...