That greater knowledge of nature by discovery of the natural causes in operation, intensifies the rational demand for recognition of Supernatural Intelligence, is the position to be maintained throughout this argument. The most rigid test of this position is to be found in the outstanding scientific conceptions concerning inorganic and organic nature, and the contrasts recognized between lower and higher organisms. The order most suitable for application of this test is progress upwards from the most subordinate forms of existence to the most complex organism. A beginning will, therefore, be male with the inorganic world, after which lower organisms may be considered, after that the relative place of higher organisms, and finally the whole class of questions concerning the powers and requirements of mind. In each of these relations, I desire to inquire into the reasonableness of our acknowledgment of the supernatural. As the world presents a vast range of inorganic existence, we have to consider the most prominent scientific conceptions concerning inorganic elements, as these afford a general view of the material structure of the earth. Concentrating on this region of observation, and taking no account, meanwhile, of the manifold phases of life, there are two forms of existence to be recognized, Matter and Energy. Matter is solid, visible, tangible; Energy is invisible and intangible, but measurable by the work it is capable of doing. The one may be represented as the solid inert mass, the other as the moving power whose action is the source of continual change. This duality we must regard as essential to the structure of the universe, for it is impossible to identify the two, so as to regard the world as merely a mass of matter. This duality is now commonly admitted as the result of recent scientific investigations. To quote the words of Professor Tait,--"It is only within comparatively recent years that it has been generally recognized that there is something else in the physical universe which possesses to the full as high a claim to objective reality as matter possesses, though it is by no means so tangible, and therefore the conception of it was much longer in forcing itself upon the human mind."[AD] This is Energy. "Just as gold, lead, oxygen, etc., are different kinds of matter, so sound, light, heat, etc., are now ranked as different forms of energy."[AE] Here, then, is one of the conspicuous results of recent scientific research to which all our thoughts and theories need to adapt themselves. And it must be obvious without argumentation, that theological thought will not experience any serious shock, or even jolt, in passing over to this new line of rails prepared for it.