Many other points in the system of Heracleitus are worthy of the closest study. Intensely interesting, for example, is his doctrine that strife is the condition of harmony, and indeed of existence. Schelling reproduced this idea in his well-known theory of polarity; Hegel developed it in his dialectic triad-- Thesis, Antithesis, Synthesis; and the electrical theories of matter and force now in vogue fall easily into line with it--not to speak of the dominant theory of evolution as involving a struggle for existence, and as applied in well-nigh all departments of enquiry and research. But it is enough to have grasped the central principle of Fire-motion to prove that the phenomena of fire have had an influence in the development of man's intellectual and spiritual life--an influence which cannot easily be exaggerated. Heracleitus claims an honoured place in the line of nature-mystics. CHAPTER XXVIII FIRE AND THE SUN There can be no doubt, as already stated, that, of all physical phenomena, fire had the most marked effect upon the imagination of primitive man. He saw that it was utterly unlike anything else known to him, both in its properties and in its action. If of anything a divine nature could be predicated, it was fire--the standing miracle--at once destroying and life-giving-- material and immaterial--pre-eminently an agent with strange and vast powers, known and unknown. For many objects and institutions a divine origin was sought; it could not fail to be the case with fire. Even the poor Tasmanian natives felt it could not be a thing of earth, and told each other how it was thrown down like a star by two black fellows who are now in the sky, the twin stars, Castor and Pollux. A great gap separates this simple tale from the elaborate Prometheus myth, and yet the same essential features appear in both: and between the two are found a varied series of stories and legends, belonging to many climes and ages, which ring the changes on the same fundamental ideas. The whole of the ancient world believed that the origin of fire must be divine. And the various steps can be clearly traced by which the worship, originally accorded to the nature-power itself, was transferred to a spirit behind the power, and centred at last on the supreme Deity.