Book 9
11.97
Causes, too, they destroy in this way. A cause is something relative; for it is relative to what can be caused, namely, the effect. But things which are relative are merely objects of thought and have no substantial existence.
11.98
Therefore a cause can only be an object of thought; inasmuch as, if it be a cause, it must bring with it that of which it is said to be the cause, otherwise it will not be a cause. Just as a father, in the absence of that in relation to which he is called father, will not be a father, so too with a cause. But that in relation to which the cause is thought of, namely the effect, is not present; for there is no coming into being or passing away or any other process: therefore there is no such thing as cause. Furthermore, if there is a cause, either bodies are the cause of bodies, or things incorporeal of things incorporeal; but neither is the case; therefore there is no such thing as cause. Body in fact could not be the cause of body, inasmuch as both have the same nature. And if either is called a cause in so far as it is a body, the other, being a body, will become a cause.
