Eight essays trace seminal ideas about the foundations of geometry that led to the development of Einstein's general theory of relativity. This original Dover publication is the only English-language collection of these important papers, some of which are extremely hard to find.Contents include "On the Hypotheses which Lie at the Foundations of Geometry" by Georg Friedrich Riemann; "On the Facts which Lie at the Foundations of Geometry" and "On the Origin and Significance of Geometrical Axioms" by Hermann von Helmholtz; "A Comparative Review of Recent Researches in Geometry" by Felix Klein; "On the Space Theory of Matter" by William Kingdon Clifford; "On the Foundations of Geometry" by Henri Poincaré; "Euclidean Geometry and Riemannian Geometry" by Elie Cartan; and "The Problem of Space, Ether, and the Field in Physics" by Albert Einstein.These remarkably accessible papers will appeal to students of modern physics and mathematics, as well as anyone interested in the origins and sources of Einstein's most profound work. Peter Pesic of St. John's College in Santa Fe, New Mexico, provides an introduction, as well as notes that offer insights into each paper.