To object here that the different reactions of the two substances are due only to the difference of their respective temperatures of ignition, and that above these temperatures the difference will more

or less disappear (all combustible substances at a sufficiently high temperature becoming more or less similar to phosphorus), would not meet the argument. For what matters here is just how the particular substance behaves at that level of temperature on which the earth unfolds her normal planetary activity. To ignore this would be to violate one of the principles we have adopted from Goethe, which is never to derive fundamental concepts of nature from observations obtained under artificial conditions.