Every science must start from two principal data. One of these is always the principle of sufficient reason in some form or another, as organon; the other is its special object as problem. Thus, for example, geometry has space as problem, and the ground of existence in space as organon. Arithmetic has time as problem, and the ground of existence in time as organon. Logic has the combination of concepts as such as problem, and the ground of knowledge as organon. History has the past acts of men treated as a whole as problem, and the law of human motives as organon. Natural science has matter as problem, and the law of causality as organon. Its end and aim is therefore, by the guidance of causality, to refer all possible states of matter to other states, and ultimately to one single state; and again to deduce these states from each other, and ultimately from one single state. Thus two states of matter stand over against each other in natural science as extremes: that state in which matter is furthest from being the immediate object of the subject, and that state in which it is most completely such an immediate object, _i.e._, the most dead and crude matter, the primary element, as the one extreme, and the human organism as the other. Natural science as chemistry seeks for the first, as physiology for the second. But as yet neither extreme has been reached, and it is only in the intermediate ground that something has been won. The prospect is indeed somewhat hopeless. The chemists, under the presupposition that the qualitative division of matter is not, like quantitative division, an endless process, are always trying to decrease the number of the elements, of which there are still about sixty; and if they were to succeed in reducing them to two, they would still try to find the common root of these. For, on the one hand, the law of homogeneity leads to the assumption of a primary chemical state of matter, which alone belongs to matter as such, and precedes all others which are not essentially matter as such, but merely contingent forms and qualities. On the other hand, we cannot understand how this one state could ever experience a chemical change, if there did not exist a second state to affect it. Thus the same difficulty appears in chemistry which Epicurus met with in mechanics. For he had to show how the first atom departed from the original direction of its motion. Indeed this contradiction, which develops entirely of itself and can neither be escaped nor solved, might quite properly be set up as a chemical _antinomy_. Thus an antinomy appears in the one extreme of natural science, and a corresponding one will appear in the other. There is just as little hope of reaching this opposite extreme of natural science, for we see ever more clearly that what is chemical can never be referred to what is mechanical, nor what is organic to what is chemical or electrical. Those who in our own day are