such justification as they may derive from similar freedoms on my part; I came to the conclusion that my best course was to leave the essays just as they were written;[8] assuring my honourable adversaries that any heat of which signs may remain was generated, in accordance with the law of the conservation of energy, by the force of their own blows, and has long since been dissipated into space. But, however the polemical coincomitants of these discussions may be regarded--or better, disregarded--there is no doubt either about the importance of the topics of which they treat, or as to the public interest in the "Controverted Questions" with which they deal. Or rather, the Controverted Question; for disconnected as these pieces may, perhaps, appear to be, they are, in fact, concerned only with different aspects of a single problem, with which thinking men have been occupied, ever since they began seriously to consider the wonderful frame of things in which their lives are set, and to seek for trustworthy guidance among its intricacies. Experience speedily taught them that the shifting scenes of the world's stage have a permanent background; that there is order amidst the seeming confusion, and that many events take place according to unchanging rules. To this region of familiar steadiness and customary regularity they gave the name of Nature. But, at the same time, their infantile and untutored reason, little more, as yet, than the playfellow of the imagination, led them to believe that this tangible, commonplace, orderly world of Nature was surrounded and interpenetrated by another intangible and mysterious world, no more bound by fixed rules than, as they fancied, were the thoughts and passions which coursed through their minds and seemed to exercise an intermittent and capricious rule over their bodies. They attributed to the entities, with which they peopled this dim and dreadful region, an unlimited amount of that power of modifying the course of events of which they themselves possessed a small share, and thus came to regard them as not merely beyond, but above, Nature.