The Philosophy of nature, like that of history, expresses itself in false analogies. It will say, for instance, that the poles of the magnet are the opposed moments of the concept, made extrinsic and appearing in space; or that light is the ideality of nature; or that magnetism corresponds to length, electricity to breadth and gravity to volume; or again (like more ancient philosophers), that water, or fire, or sulphur, or mercury, is the essence of all natural facts. But these phenomena which are given as essences, those classes of natural facts which are given as moments of the concept and of the spirit, are no longer either scientific phenomena, or the concepts and spiritual forms of philosophy. The first are intuitions and not categories; the second categories and not intuitions; and just because they are so clearly distinguished from one another they mutually mingle in the _a priori_ synthesis. On the other hand, the concepts of the Philosophy of nature are categories, which as such present themselves in their emptiness as intuitions, and intuitions, which in their blindness present themselves as categories. These thoughts are contradictory. They can be _spoken,_ or rather _tittered,_ because it is possible to combine phonetically contradictory propositions, but it is impossible to think them. Such combinations by their ingenuity often give rise to surprise or astonishment. But mental satisfaction is never obtained from them merely because the mind is excited and deluded. On the other hand, the Philosophy of nature, in this labour of ingenuity, runs against limits, which even ingenuity cannot overcome. Then are heard affirmations, which amount to open confessions of the impossibility of the task. Of this sort is the assertion that nature contains the contingent and the irrational and therefore is incapable of complete rationalization; or that nature in its self-externality is impotent to achieve the concept and the spirit. In like manner. Philosophies of history end by confessing that there are facts which are told and are not deduced, because they are small, contingent and fortuitous matter for chronicle. Thus, after having announced in the programme the rationality of nature and of history, they recognize in the execution of the programme that the contrary is true. They simply deny the rationality of the world, because they cannot bring themselves to deny the rationality of the pseudo-sciences of philosophism. [Sidenote: _Works entitled Philosophy of nature._]