Together with the overcoming of the fallacy that heat is a ponderable substance (full certainty was indeed established only some time later through the investigations of Davy and Rumford into heat generated by friction) - human thinking was led into a one-sided conception of combustion which was merely the opposite of the one held earlier. Whereas formerly man's mind was pre-eminently occupied by the liberation of the imponderable element through combustion, it now turned entirely to what goes on in the ponderable realm. As we have seen, one outcome of this one-sided view of combustion was the modern concept of the chemical element. To-day our task is to overcome this concept by taking a step corresponding to the one that led to it, that is, by a study of combustibility which does justice to both sides of the process involved. * As objects of our observation we choose three chemical elements all of which have the property of combustibility: Sulphur, Phosphorus, and Carbon. As will become clear, our choice of these three is determined by the fact that together they represent an instance 'worth a thousand, bearing all within itself. We begin by comparing Sulphur and Phosphorus. In their elementary state they have in common the fact that any chemical change is bound up with an increase in their weight. In this state both are combustible. Apart from this similarity, there is a great difference between them, as the way of storing them illustrates. For while elementary sulphur needs only an ordinary container, phosphorus has to be kept under cover of water in order to prevent the atmospheric oxygen from touching it. The reason is that the combustible state is natural for sulphur, but not for phosphorus, the latter's natural state being the oxidized one. This different relationship of sulphur and phosphorus to the oxidizable (reduced) and the oxidized state manifests itself in all their chemical reactions. 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.