Carl Ludwig Siegel quotes

I am afraid that mathematics will perish by the end of this century if the present trend for senseless abstractin - as I call it: theory of the empty set - cannot be blocked up. (Carl Ludwig Siegel)
Ours, according to Leibnitz, is the best of all possible worlds, and the laws of nature can therefore be described in terms of extremal principles. Thus, arising from corresponding variational problems, the differential equations of mechanics have invariance properties relative to certain groups of coordinate transformations. View quote
Carl Ludwig Siegel
One of the many importants ideas introduced by Minkowski into the study of convex bodies was that of gauge function. Roughly, the gauge function is the equation of a convex body. Minkowski showed that the gauge function could be defined in a purely geometric way and that it must have certain properties analogous to those possessed by the distance of a point from the origin. He also showed that conversely given any function possessing these properties, there exists a convex body with the given function as its gauge function. View quote
Carl Ludwig Siegel