ABSTRACT
In the development of science there is a constant and fruitful struggle going on between two tendencies. A very good example of this fruitful strife is found in the history of our ideas about the solar system. Kepler thought that Mercury, Venus, Earth, Mars, Jupiter and Saturn each moved in a sphere with the sun as its centre, and the spheres were so arranged that one of the regular solids would fit in between two of the spheres. Newton showed why the orbits have the shape they have, and why a planet at a particular distance from the sun must move at the speed it does. The important point is that Kuiper's work justifies the view held by all Marxists, and a great many scientists who are not Marxists, that there are no arbitrary features in the universe, that is to say facts for which no rational explanation can be found.
