Heracleitus is a philosopher whose speculations are of surpassing interest for the student of Nature Mysticism. He was born about 540 B.C., at Ephesus, and lived some sixty years. He was one of the most remarkable thinkers of antiquity, and the main substance of his teaching remains as a living and stimulating element in the most advanced scientific and metaphysical doctrines of the present day. But taking the point of view of the nature-mystic, he derives his special significance from the manner of his early training, and from the source of his early inspirations. While still a youth, he forsook the bustle of the city for the solitude and charm of the lovely country which surrounded his home, and he definitely set himself to feed his imagination on the concrete and sensuous imagery of the poets. He laid himself open to the impressions and intuitions which such an environment so richly provided, and thus laid the foundation for those speculations on the nature of the universe and of life which have rendered his influence so lasting and his fame so great. He is undoubtedly difficult to understand, and his cryptic utterances earned for him the doubtful title of the Dark. But his champions have pointed out that his obscurity of diction was not the outcome of pride or intentional assumption of mystery, but of the genuine difficulty he found in giving expression to his novel thoughts. He waxes vehement in his struggles to subdue his language to his purposes, his vague intuitions, his movements in worlds not fully realised; and in this regard he can at any rate claim the sympathy of mystics of every school. Such was the man and such his training. What was his central, dominating thought? What was his conception of the universal Ground of existence? It was this--Pure Fire--motion is the secret of the eternal change which characterises all known phenomena of every grade and kind. "All things flow" is the far-famed aphorism which sums up his philosophy. This eternal movement is not, however, formless, but is determined to ever-recurrent forms, and is obedient to law and rhythm. He taught, then, that the eternal movement which constitutes existence is Fire. "This one order of all things (he affirms) was created by none of the gods, nor yet by any of mankind; but it was ever, and is, and shall be, eternal fire-ignited by measure and extinguished by measure." But more--he held that this Fire-motion is alive. It will be remembered that Thales had placed the cause of motion in matter itself, not in something other than matter; that is to say, he was to all intents and purposes a hylozoist. Heracleitus went a step farther, and maintained that the life in Fire-motion is _organic_, like to that which is manifested in the plant and animal worlds. His idea of the essential kinship of all things is very clear and complete.