After all, what is a law of nature as such for us? We are not acquainted with it in itself, but only with its effects, which means in its relation to other laws of nature-which, in turn, are known to us only as sums of relations. Therefore all these relations always refer again to others and are thoroughly incomprehensible to us in their essence. All that we actually know about these laws of nature is what we ourselves bring to them-time and space, and therefore relationships of succession and number.