We can say in general that the science of medicine or of engineering, of jurisprudence or of education, contains, as science, no element of art, but merely theoretical judgments which, as such, can find their place somewhere in the complete systems of the theoretical sciences. If the physician describes a disease, its symptoms, the means of examining them, the remedies, their therapeutical effects, and the prophylaxis, in short, everything which the physician needs for his art, he does not record anything which would not belong to an ideally complete description and explanation of the processes in the human body. In the same way it can be said that if the engineer characterizes the conditions under which an iron bridge will be safe, it is evident that he cannot introduce any facts which would not find their logical place in an ideally complete description of the properties of inorganic nature; and finally, the same is true for the statements of the politician, the jurist, the pedagogue, or the minister. Whatever is said about their art is a theoretical judgment which connects facts of the ideally complete system of theoretical science; in their case the facts of course belong in first line to the realm of the psychological, historical, and normative sciences. There never has been or can be practical advice in the form of words, which is not in principle a statement of facts which belong to the absolute totality of theoretical knowledge. Seen from this point of view, it is evident that all our knowledge is fundamentally theoretical, and that the conception of practical knowledge is logically unprecise.