IV
In the introduction to the 'Principles of Mechanics,' of Herz[1] we find the following statement: "In endeavoring thus to draw inferences as to the future from the pant, we always adopt the following process. We form for ourselves images or symbols of external objects, and the form which we give them is such that the necessary consequents of the images in thought are always the images of the necessary consequents in nature of the things pictured. . . . The images of which we here speak are our conceptions of things. With the things themselves they are in conformity in one important respect, viz., in satisfying the above-mentioned requirement. For our purpose it is not necessary that they should be in conformity with the things in any other respect whatever." The concepts must be 'permissible,' that is, logically self-consistent; they must be correct, or not contradicted by experience; and they must be appropriate, that is, embody the 'principle of economy.'[2]
Herz, thus, in agreement with Mach and Carl Pearson, describes the scientific concept as a construction of the investigator. It is an instrument with a function, that of leading to new observations and predicting sequences of phenomena.
This point of view is, however, radically opposed to the older view which defined its aim as the discovery of the real causes of observable phenomena. It was taken for granted that the phenomena of nature depended upon movements of matter,— and that matter in motion was a definite transcendent object of knowledge. The following from Helmholtz expresses this point of view. "The theoretical portion of physical science seeks to discover the unknown causes of events from their observable effects; it seeks to understand them according to the law of causality. We are forced to this task by the principle that every change in nature must have an adequate cause. . . . The final goal of the theoretical sciences is thus to discover the ultimate unchanging causes of changes in nature."[3]
Herz himself at one time predicted that the great problem of physical science would be the nature and the laws of the space-filling ether. "It seems more and more probable that this question will take precedence of all others."[4] 'Herz spoke then wholly committed to old preconceptions,' says Kleinpeter in the article from which I take the quotation; and it goes without saying that Herz
