In order to elucidate in the first place the introduction of fire as a world-shaping force, I recall how Anaximander had further developed the theory of water as the origin of things. Placing confidence in the essential part of Thales' theory, and strengthening and adding to the latter's observations, Anaximander however was not to be convinced that before the water and, as it were, after the water there was no further stage of quality: no, to him out of the Warm and the Cold the Moist seemed to form itself, and the Warm and the Cold therefore were supposed to be the preliminary stages, the still more original qualities. With their issuing forth from the primordial existence of the "Indefinite," Becoming begins. Heraclitus who as physicist subordinated himself to the importance of Anaximander, explains to himself this Anaximandrian "Warm" as the respiration, the warm breath, the dry vapours, in short as the fiery element: about this fire he now enunciates the same as Thales and Anaximander had enunciated about the water: that in innumerable metamorphoses it was passing along the path of Becoming, especially in the three chief aggregate stages as something Warm, Moist, and Firm. For water in descending is transformed into earth, in ascending into fire: or as Heraclitus appears to have expressed himself more exactly: from the sea ascend only the pure vapours which serve as food to the divine fire of the stars, from the earth only the dark, foggy ones, from which the Moist derives its nourishment. The pure vapours are the transitional stage in the passing of sea into fire, the impure the transitional stage in the passing of earth into water. Thus the two paths of metamorphosis of the fire run continuously side by side, upwards and downwards, to and fro, from fire to water, from water to earth, from earth back again to water, from water to fire. Whereas Heraclitus is a follower of Anaximander in the most important of these conceptions, _e.g.,_ that the fire is kept up by the evaporations, or herein, that out of the water is dissolved partly earth, partly fire; he is on the other hand quite independent and in opposition to Anaximander in excluding the "Cold" from the physical process, whilst Anaximander had put it side by side with the "Warm" as having the same rights, so as to let the "Moist" originate out of both. To do so, was of course a necessity to Heraclitus, for if everything is to be fire, then, however many possibilities of its transformation might be assumed, nothing can exist that would be the absolute antithesis to fire; he has, therefore, probably interpreted only as a degree of the "Warm" that which is called the "Cold," and he could justify this interpretation without difficulty. Much more important than this deviation from the doctrine of Anaximander is a further agreement; he, like the latter, believes in an end of the world periodically repeating itself and in an ever-renewed emerging of