 diagrams |  epistemology |  Frege, Gottlob: controversy with Hilbert |  geometry: in the 19th century |  Helmholtz, Hermann von |  Hilbert, David: program in the foundations of mathematics |  Hume, David |  Kant, Immanuel |  Kant, Immanuel: philosophy of mathematics |  Kant, Immanuel: views on space and time |  Locke, John |  Locke, John: philosophy of science |  Poincaré, Henri |  Russell, Bertrand |  space and time: inertial frames |  visual thinking in mathematics: epistemology of 