In fact, primitive man may well have been as devoid of the conception of a realm of spirit as was his anthropoid ancestor. The lowest savages of to-day are almost, if not quite, lacking in such a conception, and are destitute of anything that can fairly be called religion. Where apparent religious ideas exist among them we cannot be sure to what extent they have been infused by civilized visitors, or how far ardent missionaries, in their anxiety to discover some trace of religion in savages, have themselves inadvertently suggested the beliefs which they triumphantly record. The Pygmies of Africa, the Negritos of Oceanica, and various debased tribes elsewhere, may possibly be quite destitute of native religious conceptions, at least of a higher grade than those which move the horse and dog to a dread of the unseen. It should be borne in mind that these tribes have for thousands of years been in some degree of contact with more developed races and subject to educative influences, and the crude religious conceptions which some travellers attribute to them may well have been derived, not original. Investigation in this field certainly gives us abundant warrant to believe that primitive man, on whose mind no influences of education could act, was destitute of religion, and that man's conception of the unseen arose gradually, as one important phase of the development of his intellect. Any attempt to trace the stages of this religious development is far beyond our purpose, even if we were capable of doing it. It must suffice to say that man everywhere, when he emerges into history as a semicivilized being, is abundantly supplied with mythological and other religious conceptions which indicate a long preceding evolution in this field of thought. For extended ages the realm of the unseen has been acting upon the mind of man; filling him with dread of malevolent and reverence for beneficent powers, inspiring him to acts of worship, peopling his imagined heavens with imagined deities, and giving rise to an extraordinary variety of deific tales and mythological ideas. The literature of this subject would fill a library in itself, and is almost abundant enough to supply one with reading for a lifetime. Yet it is largely, if not wholly, ideal; it is in great part based on false conceptions and misdirected imaginings; it rarely adduces evidence, and such evidence as is offered is always questionable; in short, scientific investigation and the critical pursuit of facts have taken no part in the development of religious systems, and a deep cloud of doubt envelops them all.