Remembering that our first occasion to concern ourselves overtly with the concept of polarity was in connexion with the four elements, we may now ask whether the old doctrine did not embrace some conception of secondary polarity as well as of primary polarity, and if so, whether this might not prove as helpful in clarifying our own conceptions as was the primary polarity, cold-warm. That this is indeed so, the following description will show. Beside the two qualities cold and warm the doctrine of the four elements pointed to two further qualities forming in themselves a pair of opposites, namely, dry and moist. Just as the four elements were seen as grouping themselves in two pairs, Fire-Air on the one hand, Water-Earth on the other, the first being characterized by the quality warm, the second by cold, so were they seen to form two opposing groups, Fire-Earth and Air-Water, of which one was characterized by the quality dry, the other by the quality moist. Fig. 5 shows how the four elements in their totality were seen to arise out of the various combinations of the four qualities. In this diagram the element Earth appears as a combination of the qualities Dry and Cold; Water of Cold and Moist; Air of Moist and Warm; Fire of Warm and Dry. As a result, Earth and Fire, besides representing opposite poles, are also neighbours in the diagram. Here we encounter a picture characteristic of all earlier ways of looking at the world: the members of a system of phenomena, when ranked in due order of succession, were seen to turn back on themselves circle-wise - or, more precisely, spiral-wise. In what way do the qualities dry and moist form a polarity of the second order, and how do they represent the chemical polarity characteristic of sulphur and phosphorus as well as all the other secondary polarities dealt with in this book? To understand this we must submit the couple dry-moist to the same scrutiny as we applied to cold and warm in our earlier discussion of the four elements. It lies in the nature of things that we instinctively associate these qualities with the solid and liquid states of matter respectively. This certainly agrees with the diagram given above, where the elements Earth and Water are distinguished precisely by their connexion with these two characteristics. Yet, in addition to this, the qualities dry and moist are found to be characteristic also of Fire and Air respectively, though with the difference that they are linked not with the quality cold, as in the case of the lower elements, but with the quality warm. So we see that the concepts Dry and Moist, as they lived in the old picturing of them, mean a good deal more than we understand by them to-day.