Besides, what does not hinder is separated from what takes place; but the cause is related to the event. That, therefore, which does not hinder cannot be a cause. Wherefore, then, it is accomplished, because that which can hinder is not present. Causation is then predicated in four ways: The efficient cause, as the statuary; and the material, as the brass; and the form, as the character; and the end, as the honour of the Gymnasiarch.