The method of explanation founded on purpose and aim does not, surely, suddenly begin with man and end with him. There is as much behind the exhibition of will and motive which we see in man as there is behind the phenomena of movement; they are co-ordinate, neither to be resolved into the other. And the commencement of the investigation of that will and motive which lies behind the will and motive manifested in the three-dimensional mechanical field is in the conception of a soul—a four-dimensional organism, which expresses its higher physical being in the symmetry of the body, and gives the aims and motives of human existence. Our primary task is to form a systematic knowledge of the phenomena of a four-dimensional world and find those points in which this knowledge must be called in to complete our mechanical explanation of the universe. But a subsidiary contribution towards the verification of the hypothesis may be made by passing in review the history of human thought, and enquiring if it presents such features as would be naturally expected on this assumption. CHAPTER IV THE FIRST CHAPTER IN THE HISTORY OF FOUR SPACE Parmenides, and the Asiatic thinkers with whom he is in close affinity, propound a theory of existence which is in close accord with a conception of a possible relation between a higher and a lower dimensional space. This theory, prior and in marked contrast to the main stream of thought, which we shall afterwards describe, forms a closed circle by itself. It is one which in all ages has had a strong attraction for pure intellect, and is the natural mode of thought for those who refrain from projecting their own volition into nature under the guise of causality. According to Parmenides of the school of Elea the all is one, unmoving and unchanging. The permanent amid the transient—that foothold for thought, that solid ground for feeling on the discovery of which depends all our life—is no phantom; it is the image amidst deception of true being, the eternal, the unmoved, the one. Thus says Parmenides. But how explain the shifting scene, these mutations of things! “Illusion,” answers Parmenides. Distinguishing between truth and error, he tells of the true doctrine of the one—the false opinion of a changing world. He is no less memorable for the manner of his advocacy than for the cause he advocates. It is as if from his firm foothold of being he could play with the thoughts under the burden of which others laboured, for from him springs that fluency of supposition and hypothesis which forms the texture of Plato’s dialectic. Can the mind conceive a more delightful intellectual picture than that of Parmenides, pointing to the one, the true, the unchanging, and yet on the other hand ready to discuss all manner of false opinion, forming a cosmogony too, false “but mine own” after the fashion of the time?