Who shall say how old is this idea of two distinct, and generally opposing principles, the light and the dark? The Babylonian cosmology carries us a long way back, but not to the beginning of such mystical conceptions. For in that cosmology Marduk is a well-developed god of light, with Tiâmat as his antithesis, the goddess of the dark, and the nature and course of the deadly contest between them has taken form in a well-defined series of myths. One of the most obvious emotional effects of darkness is to inspire fear, and there are few who have not in some degree and on some occasions experienced a sense of discomfort in the dark--a chill, or a shrinking, which in certain cases, especially with children, may amount to terror. It is possible that we have here, as is often contended, an organic reminiscence of the experience of our remote ancestors. Certainly it is not difficult for us to sympathise with the primitive dread of darkness, nor to understand the transition to the conception of darkness as a hostile power. But there is also an element which may be regarded as simply personal and individual--a natural anticipation of unknown dangers, and a sense of helplessness should the apprehensions be realised. There is, moreover, an element of a still more directly mystical character, that which Everett describes as a feeling that in the darkness the familiar world is swept away and that we are touching the limits of the natural. Hence the chill of the unknown and supernatural. However this may be, the fact remains that from the earliest known times, there have been powers of darkness set over against the powers of light; and the conflict between them has suggested with exceptional vividness the conflict between good and evil. The opening verses of the Bible, with their chaos and darkness, and the sublime command--"Let there be light"--are in line with a vast body of primitive myth and speculation which represents the good God as the Creator of light, or as light itself over against the dark. The mysticism of the prologue to St. John's Gospel both represented and fostered ideas which were current in the earliest Christian communities and have coloured the whole of the primitive Christian literature. So in the most ancient of the classical mythologies, Night was one of the oldest deities, daughter of Chaos, and sister of Erebus, the dark underworld. So in Persian dogmatic we have the same essential concepts. From the beginning existed uncreated light and uncreated darkness--the opposing kingdoms of Ahura and Ahriman. Who shall say what great cosmic facts lie behind these vague and looming intuitions? The physical merges by insensible degrees into the aesthetic, the moral, the spiritual. On the one hand, the chill, the blankness, the negation, sometimes the horror, of the darkness. And on the other hand the purity and beauty, the colour and effulgence of the light--above all, its joy-giving, life-giving, though noiseless, energy.