For example, when we ask how it is that there are bodies in motion, or that agitated air communicates its motion to water, or rather how it is that bodies push one another, then, since motion and its communication is a general effect on which all others depend, it is necessary, I do not say in order to be a Christian but to be a philosopher, to have recourse to God, who is the universal cause, because His will is the motor force of bodies and also produces the communication of their motion.