had assumed a fundamentally different point of view when he wrote the 'Mechanics.'
Kirehhoff in the introduction to his 'Vorlesungen über Mathematische Physik' gives expression to the new point of view. He says: "The point of departure which I have chosen is not the ordinary one. It is customary to define mechanics as the science of forces, and forces as the causes which produce motion or strive to produce motion, . . . In the cause of the precision, which is, in other respects, characteristic of conclusions in mechanics, it seems desirable to get rid of ambiguous terms (Dunkelheiten) even if we are obliged to narrow the task of mechanics. I, therefore, propose, as this task, the description of the movements which occur in nature, a description as complete and as simple as possible."[1]
One of the frankest statements that the scientific concept is a construction of the mind and not necessarily an image of transubjective things, is the prefatory note of Herz to book I. of his 'Mechanics.' It is as follows: "The subject-matter of the first book is completely independent of experience. All the assertions made are a priori in Kant's sense. They are based upon the laws of the internal intuition of, and upon the logical forms followed by, the person who makes the assertion; with his external experience they have no other connection than these intuitions and forms may have."[2]
The second book contains the application of the system of concepts to the phenomena of experience. The contrast and relationship between volume I. and volume II. of the 'Kritik der Reinen Erfahrung' are almost identical with that between books I. and II. of the 'Mechanics' of Herz. Avenarius would not and could not claim that the concepts and definitions which fill volume I. are entirely a priori constructions. But they are psychological inventions for the purposes of scientific apperception, inventions, however, which are adapted to the phenomena. But the lines of procedure of Herz and Avenarius seem very similar. Herz described scientific method as the formation and use of images or sjinbols of external objects such that 'the necessary consequents of the images in thought are always the images of the necessary consequents in nature of the things pictured.' Now critics of Avenarius have complained of the dialectical way in which his 'Kritik' develops; but such a character is inevitable if there are to be any consequences of the symbol which shall be symbols of facts. Whether Avenarius has met with any success in this effort, whether his outcome is really a logical consequence of his symbol, or whether it could have been stated with-
