3. Applying these ideas to motion they say that motion is the passage of an atom of matter from one atom of place to the next in an atom of time. It follows from this that one motion is as fast as another; and they explain the apparent variation in speed of different motions, as for example when two bodies cover unequal distances in the same time, by saying that the body covering the smaller distance had more rests in the intervals between the motions. The same thing is true in the flight of an arrow, that there are rests even though the senses do not reveal them. For the senses cannot be trusted. We must follow the reason. Maimonides's criticism of the atomic theory of matter and motion just described is that it undermines the bases of geometry. The diagonal of a square would be the same length as its side. The properties of commensurability and incommensurability in lines and surfaces, of rational and irrational lines would cease to have any meaning. In fact all that is contained in the tenth book of Euclid would lose its foundation. 4. The atom is made complete by the accidents, without which it cannot be. Every atom created by God, they say, must have accidents, such as color, odor, motion, and so on, except quantity or magnitude, which according to them is not accident. If a substance has an accident, the latter is not attributed to the body as a whole, but is ascribed to every atom of which the body is composed. Thus in a white body every atom is white, in a moving body every atom is in motion, in a living body every atom is alive, and every atom is possessed of sense perception; for life and sense and reason and wisdom are accidents in their opinion like whiteness and blackness. 6. Accident does not last more than one moment of time. When God creates an atom he creates at the same time an accident with it. Atom without accident is impossible. The accident disappears at the end of the moment unless God creates another of the same kind, and then another, and so on, as long as he wants the accident of that kind to continue. If he ceases to create another accident, the substance too disappears. Their motive in laying down this theory of accidents is in order to destroy the conception that everything has a peculiar nature, of which its qualities and functions are the results. They attribute everything directly to God. God created a particular accident at this moment, and this is the explanation of its being. If God ceases to create it anew the next moment, it will cease to be.