Heinzmann, Gerhard The foundations of geometry and the concept of motion: Helmholtz and Poincaré. (English) Zbl 1193.01030 Sci. Context 14, No. 3, 457-470 (2001). Summary: According to Hermann von Helmholtz, free mobility of bodies seemed to be an essential condition of geometry. This free mobility can be interpreted either as matter of fact, as a convention, or as a precondition making measurements in geometry possible. Since Henri Poincaré defined conventions as principles guided by experience, the question arises in which sense experiential data can serve as the basis for the constitution of geometry. Helmholtz considered muscular activity to be the basis on which the form of space could be construed. Yet, due to the problem of illusion inherent in the subject’s self-assessment of muscular activity, this solution yielded new difficulties, in that if the manifold is abstracted from rigid bodies which serve as empirical justification of the geometrical notion of space, then illusionary bodies will produce fictive manifolds. The present article is meant to disentangle these difficulties. Cited in 1 Document MSC: 01A55 History of mathematics in the 19th century 00A30 Philosophy of mathematics 01A60 History of mathematics in the 20th century PDFBibTeX XMLCite \textit{G. Heinzmann}, Sci. Context 14, No. 3, 457--470 (2001; Zbl 1193.01030) Full Text: DOI