We have assumed, and have proved, that coming-to-be and passing-away happen to things continuously; and we assert that motion causes coming-to- be. That being so, it is evident that, if the motion be single, both processes cannot occur since they are contrary to one another: for it is a law of nature that the same cause, provided it remain in the same condition, always produces the same effect, so that, from a single motion, either coming-to-be or passing-away will always result. The movements m ...