To understand this new attitude, a brief review of the history of the fundamental features of philosophical thought will be necessary.  When, long ago, man began to think upon the phenomena of nature, he was able to understand almost nothing.  In his inability to comprehend the activities going on around him he came to regard the forces of nature as manifestations of some supernatural beings.  This was eminently natural.  He had a direct consciousness of his own power to act, and it was natural for him to assume that the activities going on around him were caused by similar powers on the part of some being like himself, only superior to him.  Thus he came to fill the unseen universe with gods controlling the forces of nature.  The wind was the breath of one god, and the lightning a bolt thrown from the hands of another.

With advancing thought the ideas of polytheism later gave place to the nobler conception of monotheism.  But for a long time yet the same ideas of the supernatural, as related to the natural, retained their place in man’s philosophy.  Those phenomena which he thought he could understand were looked upon as natural, while those which he could not understand were looked upon as supernatural, and as produced by the direct personal activity of some divine agency.  As the centuries passed, and man’s power of observation became keener and his thinking more logical, many of the hitherto mysterious phenomena became intelligible and subject to simple explanations.  As fast as this occurred these phenomena were unconsciously taken from the realm of the supernatural and placed among natural phenomena which could be explained by natural laws.  Among the first mysteries to be thus comprehended by natural law were those of astronomy.  The complicated and yet harmonious motions of the heavenly bodies had hitherto been inexplicable.  To explain them many a sublime conception of almighty power had arisen, and the study of the heavenly bodies ever gave rise to the highest thoughts of Deity.  But Newton’s law of gravitation reduced the whole to the greatest simplicity.  Through the law and force of gravitation these mysteries were brought within the grasp of human understanding.  They ceased to be looked upon as supernatural, and became natural phenomena as soon as the force of gravitation was accepted as a part of nature.

In other branches of natural phenomena the same history followed.  The forces and laws of chemical affinity were formulated and studied, and physical laws and forces were comprehended.  As these natural forces were grasped it became, little by little, evident that the various phenomena of nature were simply the result of nature’s forces acting in accordance with nature’s laws.  Phenomena hitherto mysterious were one after another brought within the realm of law, and as this occurred a smaller and smaller portion of them were left within the realm of the so-called supernatural.  By the middle of this century this advance had reached a point where scientists, at least, were ready to believe that nature’s forces were all-powerful to account for nature’s phenomena.  Science had passed from the reign of mysticism to the reign of law.