fundamental reasons for the progress in a knowledge of nature which the last four hundred years have brought in their train. But it has caused us occasionally to drop into the habit of regarding natural phenomena and events as entities, apart from the great universal interrelations, and therefore not as moving but quiescent, not as changeable in their essence but fixed and constant, not in their life but in their death. And hence, just as happened with Bacon and Locke, this point of view has been carried over from science into philosophy, and has constituted the specially narrow view of the last century, the metaphysical mode of thought. For the metaphysician, things and their pictures in the minds, concepts, are separate entities, one following the other without any regard to each other, stable, rigid, eternally fixed objects of investigation. The metaphysician thinks in antitheses. His conversation is "Yea, yea; Nay, nay" and whatsoever is more than these cometh of evil. For him a thing exists or it does not exist, a thing can never be itself and something else at the same time; positive and negative are mutually exclusive, cause and effect stand in stiff antagonism to each other. This method of thought seems at the first glance to be quite plausible because it is in accordance with sound common sense. But sound common sense, respectable fellow though he may be in his own home surrounded by his four walls, meets with strange adventures when he betakes himself into the wide world of investigation; and the metaphysical way of looking at things, sound and useful as it is, under given conditions, runs sooner or later into a stone wall, beyond which it is one-sided, stupid and abstract, and loses itself in insoluble contradictions. Because it omits to notice the interrelations of the individual phenomena, their existence, their coming and their going, their static and mobile conditions, and so to speak does not see the forest for trees. We know for example, with sufficient certainty for every day affairs, whether an animal is alive or dead, but, on closer examination, we find that this is sometimes no easy matter to decide, as jurists know very well and have gone indeed to great pains to discover a rational border line beyond which the killing of a child in the womb of its mother is murder. It is just as impossible too to fix the precise moment of death, for physiology shows that death is not a single and sudden event but a very slow process. Just so is every organic being at the same moment itself and not itself. Every moment it takes up matter coming to it from the outside and throws off other matter, every moment its body-cells die and are recreated. Indeed after a longer or shorter period the whole material of the body is renewed through the taking up of other particles of matter so that each organic being is at the same time itself and something else. We find also if we look at the matter more