 It is impossible ever to comprehend through reason how something could be a cause or have a force, rather these relations must be taken solely from experience. For the rule of our reason extends only to comparison in accordance with identity and contradiction. But, in so far as something is a cause, then, through something, something else is posited, and there is thus no connection in virtue of agreement to be found—just as no contradiction will ever arise if I wish to view the former not as a cause, because there is no contradiction [in the supposition that] if something is posited, something else is cancelled. Therefore, if they are not derived from experience, the fundamental concepts of things as causes, of forces and activities, are completely arbitrary and can neither be proved nor refuted.