In Egypt it was the _Ka_ which linked “the other world” with that of living men. In Babylonia the place of the _Ka_ was taken by the _Zi_. We may translate Zi by “spirit,” but like the Ka it was rather a double than a spirit in our sense of the term. Literally the word signified “life,” and was symbolised in the primitive picture-writing of the country by a flowering plant. Life, however, meant a great deal more to early man than it does to us. It was synonymous with motion, with force and energy. All that moved was endowed with life; life was the only force known to man which explained motion, and, conversely, motion was the sign and manifestation of life. The arrow which sped through the air or the rock which fell from the cliff did so in virtue of their possessing life, or because the motive force of life lay in some way or other behind them. The stars which slowly moved through the sky, and the sun which rose and set day by day, were living beings; it was life which gave them the power of movement, as it gave the power of movement to man himself and the animals by whom he was surrounded. The power of movement, in fact, separated the animate from the inanimate; all that moved possessed life; the motionless was lifeless and dead. Man’s experience was necessarily his measure of the universe; the only force he knew of was the force we call life, and his reason seemed to demand that what held true of himself must hold true also of the rest of the world. But, like the Egyptian, the Sumerian could not conceive of life except under visible and concrete form. The abstract was still embedded, as it were, in the concrete; it could not be divorced from it in thought any more than in those pictorial characters which were used by the scribes. What we mean by “force” would have been unintelligible to the primitive Babylonian; for him life was something real and material, which had a shape of its own, even though this shape was but an unsubstantial shadow, seen indeed by the eye, but eluding the grasp. At the same time it was more than a shadow, for it possessed all the qualities of the object or person to whom it belonged. It was not life in the abstract, but the counterpart of an individual object, which endowed that object with the power of motion, and gave it a place in the animate world.