If each us had a different kind of sense perception - if we could only perceive things now as a bird, now as a worm, now as a plant, or if one of us saw a stimulus as red, another as blue, while a third even heard the same stimulus as a sound - then no one would speak of such a regularity of nature, rather, nature would be grasped only as a creation which is subjective in the highest degree. 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.