We need not raise the question whether such a mode of treatment ever correctly interprets any actual mythological conception, or whether it represents nothing other than the creation of the mythologist's imagination. This much is clear, that it leaves out of consideration precisely those mythological ideas and religious views that really live in folk-belief. Doubtless we may assume that celestial phenomena occasionally factored as assimilative elements in the formation of mythological conceptions. But such conceptions cannot possibly have been due exclusively to celestial factors, for the very reason that, even where these are indubitably present, they are inextricably interwoven with terrestrial elements derived from man's immediate environment. Consider, for example, the figure of Helios in Greek mythology. His very name so inevitably suggests the sun that this connection remained unsevered throughout later development. Nevertheless, the Greeks no more identified the god Helios with the sun than they did Zeus himself with thunder and lightning. On the contrary, these celestial phenomena were all only attributes of deities. The god stands in the background, and, in the idea which man forms of him, the image of human heroes plays no less a part than do the impressions made by the shining heavenly bodies. These various interpretations of nature mythology, therefore, overlook an important psychological factor which is operative even in elemental experiences, but which attains increasing significance in proportion as the psychical processes become more complicated, and especially, therefore, in the formation of mythological conceptions. I refer to the _assimilative fusion of psychical elements of differing origins_. No external object is perceived precisely as it is immediately given in reality. In the experience of it, there are fused numerous elements whose source is within ourselves; these partly reinforce and partly suppress the given elements, thus producing what we call the 'perception' or the 'apprehension' of the object. The process of assimilation is greatly influenced by the emotions that may be present. To the frightened person, thunder and lightning suggest a god who hurls the lightning. Such a person believes that he really sees this god. Either the surrounding portions of the sky assume, in his imagination, the form of an immense anthropomorphic being, or the thunder and lightning lead his gaze to the canopy of clouds, hidden back of which he thinks that he discovers, at least in vague outline, the thundering Zeus. To gain some appreciation of the tremendous potency of assimilative processes, one need but recall certain situations of ordinary life, such as are experienced even apart from the influence of fear or ecstasy. Consider, for example, the vivid impression that may be aroused by theatrical scenery, which in reality consists of little more than suggestive outlines. A particularly striking illustration is offered also by the familiar puzzle pictures. In a picture of the foliage of a tree there are sketched the outlines of a human face or of the head of a cat. An uninitiated observer sees at first only the foliage. Not until his attention has been directed to it does he suddenly discover the head. Once, however, he has seen the latter, he cannot suppress it, try as he may. Here again it is sometimes but a few indistinct outlines that evoke the picture. The truth is that to a very great extent the observer reads the head into the drawing through the activity of his imagination. Now, it is but natural that such an assimilation should be immeasurably enhanced under the influence of the emotions which excite the mythological imagination. As is well known, Apollo, as well as Helios, was represented by the image of the sun. This image, however, was even less adequate to embody the idea of the Greek in the former case than it was in the latter. The Greek was able, however, to imagine the radiant sun as an attribute of the deity or as a manifestation of his activity. He could see in the sun the shield or chariot of the god; in the sun's rays, his missiles. Here again, however, he had in mind the indefinite outlines of a powerful anthropomorphic god, who could become independent of the natural phenomenon according as his name was free from connection with it.